OC mc is inserted into worm I remember him getting twin tinkers to join him and they got together he had the ability to copy other peoples powers
I'm assuming this is from the English web novel Worm (which is excellent btw), but I haven't read any fan fictions.
Worm CYOA: Things to Do in Brockton Bay When You're A Bored Demigod ... ? Though it's on QQ so you need an account to see it.
I've been enjoying this worm fanfic that is in manga form called BoKu No Hero AcAdEmIa /s Baby don't hurt me