So it looks like he went off the rails in high school, judging by the translation.
Ah, Momiji, you got that wrong.Here, this should be negative, see?Ah... Awawawa......I see. She is a scientist, after all...This is embarassing! I came over so I could teach you!!...But how!?Uhhh...! Onee-chan made me study while I was absent from school!Ahhh! Sorry about that!A-Ahaha...Scientist......Heh?...Well, I was still studying properly back in middle school...