I just can see more and more sadness and frustration in the future. I have two theories here. One is that Aiji and that gurl used to go out in junior high, since he is such a flirt she got more insecure than she already seems to be and started acting all paranoid/stalker/clingy with him. Resulting in them broking up, since neither of them could be sincere with their feelings. Second theory we see that this girl is a bit insecure, shy, Aiji saved her in the past and she fell for him. Dude being a flirt didn’t really realised this or didn’t know how to cope with his growing feelings for her and never really set things straight with Arisaka. She maybe thought they were going out and one them probably did something At some point that destroyed both that “illusion” of going out as a couple and their friendship. Resulting in both of then being hurt at the end, cuz probably Aiji realised his feelings too late of something like that (totally getting the emotionally distant family vibes with this kid behaviour, or cheater parent background). While Jun was a bystander in all that or at some point was in love with Arisaka? (Not so confident on the last part being the case). Jun’s behaviour in the first chapter was probably because: wanted to protect Aiji from this happening again or because he still had feelings for arisaka? Tbh, I’m more bend to think he was trying to protect Aiji since Jun seems to be fall for Urara faster than Aiji. OR something between this two theories. To sum up, Aiji-senpai is being the king of the douche bags. And Urara the queen of the idiot party for not seeing this and not paying attention to sweet tsundere Jun🥺