Plus they also only meet again are 10 years apart from each other. So it's not like they were around each other while shin was turning in to an adult or while in early adulthood. So I think this is perfectly fine and actually adorable that they met after all that time (not on purpose) so it was fate.(≧∀≦)
I don't see anything wrong with age gap unless there's a grooming involve. And it's a matter of preferences dude, if it's not ur cup of tea then don't read it. If it's weird and it makes you uncomfortable, don't read it?
You saw how their dynamics unfold. As far as anyone knows, their romance didn't even start when they were a minor so what's up bro? You're making an issue out of something that doesn't even have any problem. You're preaching bro
If you are not confortable don't read it, I don't like age gaps either but I actually liked this because it was clear the older one never had weird intentions or even payed THAT much attention to him when he was younger, even Shin says they were just friends, but his honestly and niceness made Shin develop feelings for him. Shin is 30 now and only acted on his feelings because Seiji was single too and took the oportunity, Seiji never really thinks of him as Kid!Shin which is a bonus.
If I give a free pass to an Age gap this is def the one, everything is wholesome and well done.
I'm 32 and I'm also very critical of age gap relationships but I think its fine here as the older guy didnt see him as a romantic interest until the younger guy confessed in his 30s. It's weird if theres a possibility of grooming but theres no such thing here as they didnt even meet again until the young guy was late 20s. Age gaps when the younger one is in their late 20s is completely fine.
I can't get over the age gap...