His friend kills him, then he gets sent to another world, or the familiar phrase, "I got isekai'd". After the crisis, he finds out he's now a vampire girl, but he doesn't have that hole... yeah, that "hole". However, there are reasons for that. The secrets behind his existence can-- "So, you want to know why we're sexless beings? Instead, question me, all of us, including you; what are the origins of our existence?" "If that's so, then I'll meet the person who reincarnated me here. I'll say 'hi', then I'll know the answer." "Meeting a god? That's impossible! We should prioritize searching for the origins of monsters, especially the ones as powerful as us, the herrschers." "I know, but I want a challenge."