whats the usual saying? half your age plus seven? i think shes much less than that here. i can be pretty accepting of these age gaps but this feels like a bit much. still im glad we got an actual ending and i can finally put this on the completed shelf
The thing is the opposite since she traveled back into her younger self meaning mentally she is his age or older.
Unless people want to spew the twitter "coded" bullcrap, mentally she was a adult during the whole thing and for most part acted as such, also its kinda hard to blame him for anything since he maintained the distance even when he realized she never returned from the start since he even took a job at a different school after they graduated from primary, at most they interacted for about a year and they were separated for about a decade.
I struggle to see a problem, romances of students and teachers have long been somewhat common, the only problem would be if there was any impropriety that is something most such romances avoid to begin with and this certainly did.