The libraries in the Underworld had many books. They often ranged in topic coverage from simple stories and myths to cookbooks to the most complex spell formulae for legendary spells. Of course, the latter would often be locked behind some incredibly impenetrable barrier.

This library, however... Sin couldn’t believe her eyes.

As she looked up, her eyes felt like they were met by an illusion. A never ending spiral that constantly flowed upwards.

Shelves upon shelves of books in glass cabinets lined the inner walls of the spiral. Where they were stood, there were doorways that led to reading rooms.

A voice came from below both Rai and Sin. They looked down.

A small golem made of clay rolled around on two small wheels, “Hello there, I am Gol Em. I am pleased to make your acquaintance, mentee 1 and mentee 2. Please let me know how I can be of service.” Its voice was monotone, and for some reason it referred to Rai and Sin as mentee 1, and mentee 2.

Rai and Sin turned to look at each other. They burst into giggles.

Gol Em didn’t have a face. In fact, all it had were two yellow gems embedded within, that they thought probably functioned like eyes.

It beeped once, “Did I say something comedic?”

Rai calmed down faster than Sin, “No... it's not you... we just don’t know why you call us mentee 1 and 2.”

Gol Em’s gems brightened, “Headmaster made me so. He refers to you as such.”

Rai stifled a giggle, “Did he say which of us was 1 and which was 2?”

Gol beeped once more, “You are 1. She is 2.”

Sin’s giggles stopped. She was just a tad bit ticked off, and that showed in her facial expression, “That old man put me at number 2? Even when I outranked you on 2 of the 3 entrance exams... that’s messed up.”

Rai smirked at her, “Haha! I’m just that much better, I guess.”

Sin pouted and crossed her arms, “Hmph!”

Gol Em interjected, “How may I be of service?”

Rai crouched to face the golem face to... gems, “I’m looking for books on the understanding of mana. Does Rodrick have any of those here?”

Gol Em’s gems brightened again, “I count 8 books that meet the criteria. Would you like for me to gather them for you?”

Rai smiled and nodded.

A moment later, 8 books flew downwards from the spiral. They suspended themselves mid-air next to each other in a line. The line of books then slotted itself into a floating blue-hued translucent bookshelf.

Gol Em beeped, “The books will follow you to the reading room. Please make use of the refreshments and snacks provided.”

Rai was amazed. The process was smooth and efficient. Beyond that, it took no time at all for Gol to search for any of the possibly relevant books.

Rai tested it by walking a step forward. The bookshelf floated behind him. He smiled as he looked back at the tiny golem, “Thanks, Gol.”

Gol Em beeped, “Pleasure to be of service.”

Rai placed a hand on Sin’s shoulder, “I’ll go in that room there.” He pointed to an empty room, “If you want to focus on your spell, then you should use one of the other empty rooms and concentrate. If you want to though, then you can also join me. Up to you.”

Sin nodded as Rai went into empty room with the floating bookshelf trailing behind him.

Gol Em rolled over to Sin, “How may I be of service, mentee 2?”

Sin felt slighted whenever she was referred to as 'mentee 2'. But that wasn't the fault of the little golem here and Sin knew that. She put aside her annoyance and pondered. There were many different ways to ask for invisibility spell tomes. It would probably be useful if I can find some books that explain invisibility before I try to learn it as a spell. Even my tutors back at the Castle would tell me to try to understand something before learning it as a technique.

She crossed her arms and tilted her head at the little golem, “Does the headmaster have any books or tomes that focus on the invisibility spell?”

Gol Em whirred for a moment. Then his little gems glowed bright, “I count 2 books and 1 tome on invisibility. You have the authority to use the tome. Would you like me to gather the books and tome for you?”

Sin smiled to herself and nodded.

In a similar fashion to how Rai’s books came to him, Sin’s books flew downwards from the spiral and settled themselves in a floating translucent bookshelf.

Gol Em beeped, “The books will follow you to the reading room. Please make use of the refreshments and snacks provided.”

Sin crouched down and patted Gol Em’s head, “Thank you Gol.”

Gol beeped satisfactorily.

She made her way to the empty reading room besides Rai’s.

More than anything, Sin wanted to focus on her goals right now. Rai would probably end up being a distraction somehow.

As the both of them settled into their rooms and prepared to read their books, they began their research process.

 

---

 

Rai started with a couple of the smaller books to see if there was any concentrated information within them, like the two books he’d previously read. Unfortunately for him, after about 20 minutes of skimming through them, there wasn’t a single mention of what he was looking for. Since the journal from Vitria's friend mentioned something about mana’s ‘counterparts’, Rai searched for that. In the smaller books, at least, he'd been left wanting.

Rai was still impressed at the depths to which these books managed to explain mana and its importance to the world. They often got the message across that people could use their mana channels to control mana, and use it to make their lives easier. By explaining it in depth, it allowed people to break down mana usage and reverse engineer it for themselves and their own understanding.

Books like these were amazing to Rai.

Even though it was amazing, it was also wholly useless to Rai considering it wasn't anywhere close to the thing that he was looking for.

The bigger books were no different.

They discussed about the basic understandings of mana, but none of them had any of the insight that Vitria’s friend had.

After combing through all 8 books, Rai furrowed his eyebrows as he leaned back in his chair. That’s... frustrating. I really hoped that there would be something useful for me here. I mean, after going through 8 books, there’s nothing?

Rai sighed. They’re so lacking. I hope Sin’s having a better time. Actually, I’ll hand these back and go check on her. I think it’s been about an hour now, so she’s probably at least read through her books.

Rai used telekinesis on the books and placed them into the translucent floating bookshelf. He walked out of the reading room and walked over to Gol Em. He crouched down and tapped Gol Em on the head, “Gol, I’ve finished reading these, could you put them back for me please?”

Gol Em beeped, “Very well mentee 1. Were they satisfactory?”

Rai rubbed the back of his head, “Not... really. They didn’t have what I was looking for.”

Gol Em beeped curiously, “What were you looking for?”

Rai shook his head, “None of the books happen to know about ‘mana’s counterparts’, would they?”

Gol Em whirred. It then leaned downwards in a somewhat depressing way, “None of the books or tomes contain such a term. My apologies mentee 1.”

Rai waved Gol’s concerns away, “Don’t worry about it. I’ll find out more about it some other way.” Rai said this, but he didn’t really know of any other way to find what he was looking for. If it wasn’t in the headmaster’s private library, then how would he be able to find it?

Maybe some clues will reveal themselves in time. I just have to be patient.

Rai found some solace in his thoughts, but he still lamented over today's failure to find anything useful for himself.

As the books flew upwards and returned to the spiral, Rai walked around and checked the reading rooms with open doors. They were all empty. He then knocked on the only other reading room with a closed door, “Sin, you in there?”

No response.

Rai knocked again, “Sin, I’ve finished up, and the period’s almost over. We should get going.”

No response.

Rai knew that this was the only room that she could be in. He sighed as he shook his head. If she's playing a prank on me, then I at least hope it'll be funny. He grabbed the door handle, “I’m coming in.”

Rai opened the door. The room was mostly empty.

The table had 2 open books on it, and a half-empty glass of water. The chair was pulled out from under the table.

Rai looked at the chair and table quizzically. So she was sitting here, and now she's not? But I can't see her.

He quickly scanned the room, only to find that it was lacking another person besides himself. Yep. Definitely can't see her. Maybe there's a clue in the books?

Rai walked over to the table and started looking at the books. Nope, nothing useful here. Where could-

Darkness enveloped his vision. The feeling of gentle hands softly holding his head was unfamiliar to him, but Rai could tell that he was in no immediate danger.

A giggling sound came from a girl behind him, “Guess who?”

Rai smirked. So that's where she was. He welled up with pride. She did it.

 

---

 

Sin laid out the 2 books and 1 tome in front of her on the table.

The tome was quite literally just called ‘Invisibility Spell Tome’.

She frowned. A little on the nose... I thought that such a valuable book would at least have a fancy title. Or at least something more interesting than that.

For now though, Sin pushed the tome aside. First, she wanted to focus her attention on the other two books.

They were small, and not as fancy looking as many of the other books she’d seen explain magical concepts before. In fact, she found it refreshing that they were simple books without much extravagance to them.

The first book was entitled ‘Complex Magical Theory’ while the second was entitled ‘How Invisibility Actually Works’. She looked at them with a hint of cautiousness. It’s a bit surprising that there are so few books on invisibility. I hope I don't get in trouble for reading these. Ah, well. It should be fine. If I was allowed to take the tome then I'm probably allowed to read these. She reassured herself.

For a moment, Sin spent thought about all of the times that she’d heard mention of the invisibility spell. My tutors from the Castle didn’t mention it much, but whenever they did talk about it... it always felt like they placed the spell on a pedestal. Why did they practically worship this spell? Is it that powerful?

I suppose it’s time to find out.

Sin was fired up. She decided to begin with the book that had the generic title, 'Complex Magical Theory'. Sin skimmed through it and searched for any mention of invisibility.

Starting with this book was a mistake. Her supposed 'fire' was now a dying flicker of embers that felt rather dejected.

She skimmed the book a second time. The result was the same. It had mentioned invisibility only a single time. All it said was that invisibility couldn’t be learned to a tier lower than legendary, even though there were variations of invisibility based on one's understanding.

This was very much unlike many of the other spells that Sin had heard about. Even telekinesis could be learned to a tier lower than what most people would recognise it for. Though, most lower tiered versions of telekinesis were just magnetism in some form or another. But when it came to invisibility, the only thing that she'd learned from this book was that invisibility was a technique with a fixed tier, regardless of its variations. I guess that invisibility is such a powerful technique, that all of its variants are just as powerful? That would make sense, since there are so many applications for invisibility.

After reading the book, Sin felt so very glad that she’d learned telekinesis in its rawest form. What Sin did not know, however, was that her understanding of telekinesis was far greater than simply its rawest form.

Regardless, she left the first book open and pushed it to the side.

Sin opened up the second book. 'How Invisibility Actually Works'.

She read through it once. Since it was so short, Sin didn't even have to skim through it. There were only a few pages, after all.

After checking the timepiece on the wall, Sin was surprised to find out that she’d read both books in only 10 minutes. Though it made sense given that the first had no useful information to focus on, and the second was so short with only a few pages. Fortunately, this book was far more useful. It detailed the differences between something known as transparency, and true invisibility. The book noted that both were some form of invisibility, and were legendary in tier.

Sin read about the variations in further detail. According to the book, the traditional understanding of invisibility is simply the ability to become transparent. However... what? How’s that even possible? True invisibility is the ability to, at will, conceal one’s presence entirely?! That’s... fucking crazy...

Sin let her head fall face-first flat onto the desk.

How am I supposed to learn this?!

She sighed.

Sin digressed. She only had one more thing left to check now.

The tome.

Sin had never used a tome before.

She didn’t even know how they worked.

Will it tell me how to use the spell? Or will it have some kind of hints about how to use the spell?

As her mind rumbled onwards, Sin took a cup of water from the refreshment table and brought it back to where she was sitting. Sin took a sip of water in preparation.

She steeled herself.

Sin opened the spell tome.

Somehow, it disappeared.

Huh?

Sin tapped the table where the tome once was. It wasn’t invisible.

HUH?!

She checked the timepiece on the wall.

20 MINUTES HAVE PASSED?! THE FUCK?!?!

Sin swore that she'd only checked the time not even a minute ago, and somehow 20 more minutes passed.

Then, she got hit by an extremely painful migraine.

Sin couldn’t move for a while. It felt like new information invaded her mind and looked for a place to settle.

After the pain subsided, Sin wiped the tears that involuntarily flowed down her cheeks and sat back in her chair. She took sips of water to refresh her brain.

What... the fuck was that? And where did the invisibility tome go?

Sin’s vision shifted. It was like she was looking through a thin filter at the room around her. She wanted to panic, since something completely random was happening to her. But Sin managed to keep herself somewhat calm. What the shit is going on... Her mana was slowly being drained.

She looked at her hand.

It wasn’t there.

Instead of screaming, like she normally would have done, Sin kept trying to stay calm. Relax. Relax Sin. Relax. It's fine. We're fine... Phew. Did the invisibility spell get absorbed into my brain or something?

The thin filter-like view dissipated. She could see her hand again.

Sin’s eyes widened. No... No way. Invisibility?

The filter returned, and Sin’s hand went invisible once more.

Sin's panic was slowly morphing into joy. No fucking way... Is this how tomes are supposed to work?! Invisibility!

Sin released the spell again. She internally screamed. After a few minutes of turning the spell on and off again, Sin left the room.

She walked over to Gol Em. Sin crouched and tapped Gol on the head, “Gol... how do magical tomes work?”

Gol Em whirred for a moment, “Tomes will instantly teach you the spell on their description to the level that your understanding dictates. The tome will disintegrate upon doing so. Tomes can be found in...” Sin disappeared entirely. There was no sign that she was ever there in the first place. Gol's gems dimmed as the tiny little golem wheeled around the room looking for her, “Mentee 2? Mentee 2?? Where did you go mentee 2? Is Gol Em malfunctioning? Gol Em swears that mentee 2 was right there.”

Sin reappeared.

Gol Em beeped twice, and continued, “Tomes can be found in numerous locations. Many of those locations are often fraught with danger. Gol Em recommends against exploring such locations.”

Sin nodded. She tried really hard to stop herself from laughing at the outcome of her going invisible. After a moment, she smiled at the little golem, “Thanks Gol. Did the headmaster mean to leave behind the invisibility tome?”

Gol Em beeped, “Gol Em does not know the answer to your question.”

Sin thought as much, “That’s fine Gol. Thank you again.”

Gol Em beeped again, “Gol Em is happy to be of service.”

Sin returned to her reading room.

She squealed as she fist pumped the air and twirled at the same time.

“This is so AWESOME!” It’s so cool! I know invisibility now!

Sin turned invisible.

She released the spell and pouted, “That’s... gonna be annoying.”

Sin returned to Gol Em, “Gol, how do I not accidentally activate a spell when I think of its trigger word?”

Gol Em beeped 3 times, then turned and looked up at Sin, “Intent, mentee 2. One must not intend to cast the spell, then the spell shan’t cast.”

Sin stared blankly at it, “I see. Thank you.”

She returned to her room.

Sin sat on the chair. She slowly allowed herself to sink into it as she racked her brain, “I don’t see how that makes sense...”

Sin thought about it for a while. Soon after, she tested it. After a couple of failed attempts and multiple minutes of thinking, she had a breakthrough.

Without the intention of becoming invisible, Sin thought the word.

Invisibility.

She didn’t become invisible.

Sin facepalmed. IT’S THAT EASY?! That only took me a few tries... Her facepalm quickly turned into a prideful grin. I’m so awesome.

Sin huffed as she puffed herself up.

After a few minutes of testing, she heard Rai’s voice from the main room.

A knock came on her door.

Rai said something.

Sin grinned. This will be fun. Invisibility.

Sin turned invisible.

After a few more knocks, Rai opened the door.

He looked around the room, then walked over to the table.

Sin softly placed her hands over Rai’s eyes and released the spell. “Guess who?”

Rai thoughtfully placed a finger on his chin, “Is it Kallad?”

Sin turned him around, “Is Kallad this cute?” She cringed heavily at her own words.

Rai cringed as well, “Please never say that again.”

Sin nodded with a cringed frown, “Yes sir.”

Rai quickly changed topics to avoid the second-hand embarrassment, “You mastered the spell?”

Sin grinned at him. She quickly shifted from being invisible to not being invisible. She put on a prideful face as she posed with a full ego, "I'm just the best."

Rai stared at her with nothing but admiration, “Your presence... it’s also disappearing as you become invisible. That’s so cool! You really are the best!”

Sin nodded profusely, “I mean, jokes aside, I have no idea how I got this lucky! The headmaster just left a spell tome laying around like that. It was weird though... I read the tome and then just blanked out for twenty minutes.”

Rai put on a thoughtful expression, “Maybe that's how tomes work. I haven't used one myself either, so I wouldn't know."

Sin's face softened, "Yeah, I asked Gol and he explained it. But I don't get how I didn't even feel the time go by; you know? It was so weird to see that twenty minutes passed, and then the tome was just gone."

Rai stretched his arms up, "Well. At least you know the spell now." He smiled at her. Then, his smile turned into a worried frown, "What if Rodrick didn’t mean to leave the tome lying around here?”

Sin raised a finger to her lips, “... We don’t know that.”

Rai stifled a giggle, “Fair point.”

Sin stretched in the same way as Rai did, “What about you? Did you find what you wanted?”

Rai shook his head with a sad face, “Nope. I zoomed through 8 books and found nothing useful. They talked about all of the basic stuff that we already know, but none of the books had what I was looking for.”

Sin frowned at him, “Damn. Maybe you’ll find what you’re looking for somewhere else. Sometimes the stuff we look for will find us, rather than us finding it.” She tried to look at the possibilities rather than dwell on the failure.

Rai nodded in agreement, “That’s what I feel as well. Anyway, let’s get packed up and leave. Don’t want to be back too late.”

Sin smiled at him, “Alright!”

She picked up the two books and put them on the bookshelf. They returned the books to Gol Em.

Rai pushed a button that opened a portal in the middle of the room, and they waved Gol Em goodbye as they left.

Rai and Sin thanked Rodrick for letting them into his library, while conveniently leaving out the part about the spell tome.

It was just after the end of school time that they left the Academy.

Sin smiled to herself as they walked. She got to learn a new spell that would be very useful as a new part of her arsenal.

She was also excited to experiment with Sinful Domain with Rai when they got back to the Secret. I hope it’s not too difficult to evolve. I really want it to evolve. How cool would that be?! She squealed with excitement and anticipation.

Rai hoped the same. He thought it would be really cool if the two of them had their own evolved forbidden techniques.