Am I missing something about him angsting over her being in middle school? If I read chapter 3 correctly we're look at two years age difference max, possibly only one*. That seems like it would be grounds for being teased by your classmates a bit at most (which is what actually seems to be happening) not being arrested (which he seems to be seriously afraid of). Am I supposed to think he's overreacting?
*If I read correctly she is explicitly 14 and he is in his first year of highschool without a defined age which according to what I looked up for the Japanese school system puts him at 15 or 16.