Well, after debating with myself on what to pick, I decided on option number 2(Accidently turning into a monster).

Now, for the main issue. What monster would you prefer our impotent mc to turn into?

1. A generic incubus: After an accident, you accidentally and miraculously transformed the origin of your being into that of an incubus, a demon that belongs to the nine hells. Now, you will go through a metamorphosis, gradually turning into an incubus and a growing sense of hunger that can only be sated through sex. If you don't get fed enough, you will slowly succumb to the beast inside you, turning into a violent animal that can only kill and rape. Racial abilities that can be gradually unlocked through absorbing sexual energies: Superhuman strength/agility/stamina/vitality, Sexual/lust empowerment, Sex/lust magic affinity, unique sexual abilities, supernaturally attractive looks, soul drain, life drain, illusion affinity, mind magic affinity, demonic physique, body modification, etc. Have the potential of becoming ascended incubi, turning an incubus into a creature of sexual love, instead of a vile creature of pure dark lust, but the method has been lost to time.
2. Special transforming sex monster(An original idea): Congratulations on fucking up on turning your dick bigger, and instead, blowing up the whole lab, leaving nothing but a scant few scraps of cloth. Everyone thought you are dead, but little did they know that you were, in fact, now transported a few miles away from town, and turned into an extinct and evil special monster that can only take the forms of, you guessed it, SEX MONSTERS!!! However, you can currently only transform into a goblin. But fear not, for you can also transform into other, more powerful forms as well... If you gather enough "energy points". How do you get it, you might ask? There are two ways. 1. Kill things(But enlightened races strangely give 10 times more points for the same effort). 2. Fuck women(Diminishing returns over the same female, but worth 3 times more than killing her initially. Virgins are worth even more). Also, you find out that, by "leveling up" your form, you can "carry over" 10% of the raw power obtained to your other forms(No skill carry over, and your "level" will change to the level of your new form.). Now then, your current goals are to survive and get the incubus form and reintegrate with society, but it is morbidly expensive... What to do?

There will be some minor game elements, like an imaginary "status window" and "system shop" as you may call it, though it is more of an innate instinct on how to spend his energy on self-improvement. It won't play a dominant role in the novel, anyways.

Now, what do you prefer?