I do not mean any offense but when I saw this section, it just reminded me of the light novel series of Toaru Majutsu no Index where the protagonist had the same experience.
The amnesiac character is a well worn trope. The interesting thing in
Golden Time is what she does with it. The majority of the time, the amnesiac wants to regain his/her old memories. In Banri's case, he fears those old memories returning, because that would mean the end of the self he has become.
There are several indications that he can tell by the way his parents and others who knew him before the accident treat him that his behavior is significantly different from before. In a very real sense, he is a new person, with different interests and a different outlook on life. He likes the life he is building for himself while living on his own in Tokyo, going to college, and in particular, getting to know Kouko. He fears that, at any time, his old self could return and erase his current existence. He also hates the constant feeling of rejection he feels from his family and others, as he gets the impression that they want the old Banri back and it makes him feel unwanted. The use of trope-defined characters, but with a level of depth beyond the norm, really makes the work stand out!