Schoool. . . Damnnn i feel old.
Also, in his flashback. He found her dead. But on her flashback, she clearly remember he drive his sword to kill her.
Does he kill her or not. . ..
Yeah, that's what feels off for me too. but so far, It did look like "he" didn't kill her but more like failed to save her. his "yandere" side in this chapter also direct to "the others who close with her" instead of her too.
We got julian and her chamberian who is most likely the one who send twins assassin to FMC and from what the twins said, he's also have yandere eyes like cyrus so it's gonna connect the dot somehow.
A few chapter ago while they're dating and he asked about "do you know about spell" then surprising when she said she didn't know. I guess it's might be some sort of ..... mental spell(?) in play. like, he got mind controlled to kill her by some keyword.
or some kind of illusion and the one who killed her is actually someone else. maybe julian's chamberian who haven't show face yet or his brother in disguised of him? (since we only know these 2 for now, I doubt her dogs could pull it off ) and then "fake cyrus" yandere side went berserk when FMC told him that cyrus and julian is indeed love each others while she's lashing out.
Because at early chapter(I reread it) there's the part where FMC saw "secret meeting of cyrus and julian" then surprise how fast he come to meet her after that so the "cyrus" she saw could be fake one? and it might be her misunderstanding + julian did gaslight her + she got killed by "cyrus" that make her belived that cyrus isn't in love with her , which contradict to his flashback that he loved her since childhood.
Just my wild guess tho. so it might not even close to target lol.