I think here the point is to show just how
strongly both of them fell in love at their first meeting. She's fine with his marriage proposal if he'll wait two years for her to graduate, and he's fine with waiting those two years. That's a pretty intense love at first sight.
Also, second year
high school means she's at least
16. That's not remotely pedo, and he could probably marry her immediately if her parents agreed (which of course they wouldn't):
For example, the effective age of consent in Tokyo by local statute is 18. The age of marriage is 16 for girls and 18 for boys with parental permission, and 20 otherwise (as stated in " ナス邃「窶慊カ窶「ナクナスニ停?邸", the Child Welfare Act of Japan.
If you're going to rage about age gaps, at least learn your definitions.
"Pedophilia is used for individuals with a primary or exclusive sexual interest in prepubescent children aged 13 or younger."