Something terrible is going to happen to the Ex isn't it? 💔
Not a SINGLE character in this story is in a good state of mind so she's next.
I can imagine her moving away or someone escaping but considering she still hasn't been stabbed yet, maybe she gets hurt that'd push the male LI over the edge (That said in the first chapter flash forward, he had somewhat long, unkempt hair so i assume other stuff has happened like either him being even more injured or kicked off the team to where he became a shut in , assuming the author is actually going to go back to the original scene unless he changes it, tho i imagine they wouldn't unless they got axed or wanted to end it soon on top of some 'epilogue' of ppl reacting)
I still don't trust Nana or anyone in this manga....
Or she is that good in fooling us
I mean she seems normal/could've easily just ignored her but hopefully she doesn't end up being collateral damage, bc at that point i'd just avoid any ex (pretty sure Nana doesn't go to the same school?) tho assuming it's Narumi? on the first page in that flashback/memory maybe he'll be back in the picture and also hurt someone for Kanae's sake again
(tho her saying 'there's no way you can understand other ppl's feelings', while that's true to an extent, just hearing someone say that almost makes it seem like they didn't rly try or so but teens, esp teenage boys prolly would be stubborn/too emotionally constipated to be vulnerable with ppl even their own partners), but Nana would probably belong in a lighthearted manga like this