Snake waits for him to get out of the shop and they talk. She just wants to know the cause of his aversion to her specially now that she remembers who he is. She absolutely doesn't give a fuck or care about the "bullying" and suprised its due to something trivial like that. She thought it was something more important. She apperantly just befriended him in the past because it would make her look good since he was a loner. She probably took it personally that he was actively avoiding her while she has her perfect facade on and thought that he could actually see through it.
She says she will leave him alone but MC asks her to stay away from FMC as well but she says "its impossible" so there is something going on there. She just leaves afterwards.
She constantly has that shit eating grin on her face as well. She seems extremely sociopathic.
He bumps in to FMC on his way back and she lifts his spirits with some peptalk which causes him to realise he loves her.
Rest of the chapters are about a cliche beach episode with dude bros, FMC and the loli.
I might have misinterpret some point so raws here;
https://ln.senmanga.com/kusunoki-san-wa-koukou-debut-ni-shippai-shite-iru
Edit. I have read spanish ones as well and oh boy. She is definitely fucked up in the head. And there is a hint about her doing compansated dating (it might be something different but it legit looks that way)
For her backstory; due to some trivial shit during elementary school, she decided that it is way better to manipulate people to be on her side. If this is authors idea of a "sad backstory" it is pretty terrible. Hopefully there is more to it. I can see the redemption arc coming from a mile away.
Her interest in the FMC looks like due to her being truely pure hearted. Like an idol she like during her childhood. She doesn't believe someone can be this naive and pure and looks like she wants to find out. Hopefully she doesn't try to brake it.