It both worked out that he started having a fling with the sunbae cuz if not they never would have even gotten together since he wasn't even into him at first but on the other hand had he done what he'd done to all his other exes he wouldn't be feeling so insecure cuz that time, knowledge, trust came with him waiting to have sex with his exes to see if they were even worth being a bf if they weren't any good. If it wasn't for the fact they have had sex and they met normally and he gave him a shot i brt he would have just broken up with him for his lack of availability
It both worked out that he started having a fling with the sunbae cuz if not they never would have even gotten together since he wasn't even into him at first but on the other hand had he done what he'd done to all his other exes he wouldn't be feeling so insecure cuz that time, knowledge, trust came with him waiting to have sex with his exes to see if they were even worth being a bf if they weren't any good. If it wasn't for the fact they have had sex and they met normally and he gave him a shot i brt he would have just broken up with him for his lack of availability