I actually find the second amnesia interesting because of the way Haru reacted very differently to Ren. Since the first time they met, even if it took a while Haru always thought of Ren as cute. But after the second amnesia he's wary of Ren and thinks he's unlikeable, and even avoids saying his name at first.
It could be because Ren is older now so mentally Haru thinks of Ren as someone his age, but I think it's also because the first time they were introduced and the first time Haru had amnesia Ren was introduced as his "little brother" while this time Ren outright admitted to having special feelings for him. Also despite not remembering why, Haru still couldn't reject Ren mentally so it might have freaked him out. That was quite a wild way of figuring out you're gay. Lol
this is too precious, too good, too pure for this world T^T