who is the other guy in cover

Want spoiler?

Yes

Basically, the uke will got into a accident and lose his memory, and this mf in the cover met him in the school and yk trying to have him, and the merman trying to let him remember him, but he will end up with the merman don’t worry (⌒▽⌒) (but if the uke will do it with that guy or yk, I’m dropping this.)