I was just thinking how this was an interesting series when I noticed it was death toll translating. Thank you guys for always picking up some interesting manga
So, her boyfriend and male friends all had alibis. Therefore it must've been someone whom she wasn't acquanted with. The victim wasn't acquainted with any women then I guess?
Let's see how long until the protagonist becomes annoyingly a moralist, I've dropped all of this author's works before because of this, even though they had great concepts.