The situation between Minato & Koyun actually has a lot to do with Momoka btw. Koyun is hesitant because of what she heard Minato say about only liking her as a friend. Which he said because of the lie Momoka told him about Koyun. So he doesn't want to risk their friendship and is trying to hide his feelings. Instead it causes him to test Koyun whom he doesn't know overheard that conversation so she is also no hesitating and trying not to put Minato in a hard spot and risk their friendship. So Koyun here was actually nervous and didn't want to get her hopes up and misunderstand thinking he was asking for more. The entire situation they are in stems from the manipulation and lies Momoka told. Koyun & Minato have their issues as well, but if it weren't for the lies and manipulation and what it led to being overheard and them holding back because of it, they would have progressed already. So defending Momoka and acting like she is doing normal teenage stuff or acting like she isn't the cause of it mostly is false