I didn't really understand it either until I read the novel, but Jo Yeon-o (the blond guy) has just massive cognitive dissonance. When So Gi-hyeon (black-haired guy) confessed he only agreed to date, because he didn't want to lose him as his best friend and actually started resenting him for ruining their friendship and confessing although he knows about Jo Yeon-o's trauma regarding alphaxbeta relationships, although Jo-Yeon-o also has a crush on him, but is too stupid to realize it. So, they aren't really together just in name
Yes, but his bitch ass is stupid like he even planned their graves to be next to each other like a sap and was thinking about him day and night and then had the nerve to be mad that his crush was confessing to him, but it's not 100% clear if he was just too stupid to realize it or disregarding his feelings in favour of their friendship or disregarding his feelings due to his trauma regarding alphaxbeta relationships or betas in general. Although I think it's a mix of all three

BRO, JUST TELL EACH OTHER WHAT YOUR PROBLEMS ARE??? YOU'VE BEEN TOGETHER FOR 7 YEARS! THIS IS FRYING ME!