While it may not be much for other people, wataru's fear is valid. Being dumped/broken up because of your personality several times is enough to be scared to get in a relationship with the person you treasure the most. He must be scared that he won't be enough for Minato as a boyfriend and they will end up breaking up. He's his bestfriend and he'd rather stay friends than end up destroying their relationship.
While it may not be much for other people, wataru's fear is valid. Being dumped/broken up because of your personality several times is enough to be scared to get in a relationship with the person you treasure the most. He must be scared that he won't be enough for Minato as a boyfriend and they will end up breaking up. He's his bestfriend and he'd rather stay friends than end up destroying their relationship.
PS. Lil boss is so cute.