That girl's face in the last page. She has the face of a murderous intent (of ingesting a few million of sensei's sperm cells). In other words, "OH FUG :D"
Last page is his reward for being a gentelman. Now he can actually tell her his lines of pages 8 and 9, Happy ending. That, or she goes full yandere, Either case, it's a win,
OR
a+b, he tells her the "if you still think the same after grad we'll talk" AND she goes full yandere. FULL WIN.