It’s a rewrite of Rehammer, which means the start is mostly the same with some small changes. Chapter 15 is the first fully new chapter of the book. though Chapter 14 has a large addition. You effectively can skip to that and not missing any

(DB) A ‘normal’ teenager was watching Mumei, until an ad popped on his screen, now trying to get rid of the ad ask ”Want to have an adventure?” (A/N: Doing for fun, And this one turned one of my favorites to work on,