![](https://pic1.mangapicgallery.com/r/avatar/29/u1228899_50x50.jpg?2)
I mean who said so? If he falls in love with her in the present time it's acceptable because as you said so they only spent 3 years together and if his memories about her turned to a different direction of affection then its alright coz there aint real blood connection between them. You guys always follow society's standards of boxing certain ways to fall in love and dictate how other people can't fall in love this and that way which is from a limited mindset. People can't control who they fall in love with and who are you to judge about their feelings if those emotions doesn't really harm anyone. So if u don't like where the story is going if they become a love interest you can just drop it. Why involve yourself with something opposed from your belief.
For anyone saying this might be grooming umm no. They just spent a few months together and they got apart. So if they fall in love in the present it would be acceptable i guess, all those years of the ml going through puberty and shiz they aint together.