Holy crap that bait and switch was AMAZING! I was about to go "At this rate I'm going to drop this harder than baby Hitler off the side of a skyscraper" but then... no, I'm getting hot genderswap Dexter instead.
Yeah, it's absolutely one of the edgiest of edge edge mangas I'd ever seen. But thing is, like with kitchen knives, edge can be good if it has a distinct purpose for being so. Edge for edge's sake is irritating and immature. Isekai Dexter, though? I think it'd be much worse for it without an extreme edge.
Almost as edgy as american kirby. On a second note why not just make the mc a girl from the start lmao, feels a little pandering
Twenty five years ago, I'd have never thought genderswap could be considered pandering except to a tiny tiny niche. What a glorious age of TS we're living in now.
But to your point... One? There are only a handful of female serial killers throughout history. They exist but not even enough of them to fill out a whole page in a Wikipedia category. So it's less of a suspension of disbelief if the MC is male to start with. Two? It fits the isekai theme of reincarnation to become a completely different person.