So recently my eldest son has been interested in anime including naruto and my hero academia. He had recently become obsessed with the naruto character Sakura Haruno. He's been watching videos and cosplays of her online, searching things up about her and keeps talking about her to me. He now also wants to cosplay as her.
Does anybody know how to tell him to calm down about his obsession without offending him.
Random idea not based on any experience, but have you thought of trying to get him interested in doing other things with this? At the moment he's got all this enthusiasm but not much of a use or outlet for this besides watching videos and talking, which isn't what you'd call a very nutritious way to spend your time. Like he could try drawing her and other Naruto scenes and characters. If he throws himself into that with as much enthusiasm as he's showing for talking and watching videos, he might be quite a decent cartoonist by the time he loses interest in Naruto and moves on to the next thing, which can't be a bad thing. And while he's drawing he wouldn't be bending your ear about it :-D
In general, strong interests should be seen as a learning opportunity. Going deeper into most subjects and really understanding all its aspects can lead to developing all kinds of skills, artistic, social or otherwise. Hence people ending up with PhDs in Buffy.
I agree. A lot of the autonomous-home-education books talk about this - just for kids in general, not particularly in connection with autism - if they're interested in something see how much education you can get out of that since they'll be happy to do things if it involves that. It seems to work pretty well.