Friends that (possibly) copy my interests and try to beat me at it make my blood boil (vent?? maybe)

I'm not sure how to word the title 

Let me know if i'm overreacting im so lost rn help

Back in november, i met a mutual in a group chat. He was a friend of my cousin so i was glad to meet the people She usually hangs out with, as i worry a lot about her and her relationships with others. However, as time went on, this guy tries to pick information out of me every once in a while. It was only a occasional thing, so i didn't think much of it. He soon starts playing the same games i play and watching the same shows as me. I just thought he wanted to have something to talk about or to share a interest, and its not like i could stop him. If anything, i was actually pretty happy that he was inreacting with my interests. 

So let's call this guy "M"

However, soon M starts making it his whole personality. Literally everything i like, he'll copy. II didn't want to accidentally falsely accuse him of anything, so i just didn't say anything. he changes his profile picture to media from my favorite game, although he didn't play it, or read the story it came from. That made me a little angry, because it came from a actually meaningful story and he was just ignorning that fact.

I actually engage in oshikatsu culture. Oshikatsu is a way of actively supporting your favorite idol, character or actor (known as your oshi) through daily habits like collecting merchandise. My favorite/oshi is An Shiraishi from PJSK and she has been my oshi for about 4 years. All my friends know about my obsession with her like it's a known fact. About a week ago, M started to play pjsk for some reason. I was okay with that, because it's just a game. However, he starts making my favorite character his whole fucking personality. I would be okay if it was just his favorite character, like i have no problem with him liking what he likes, but now it's all he talks about! I am fucking fuming this kid dosent even know her birthday 

I'm sure most of us has those friends who will take funny pictures of you when you're like, blinking or somthing. M somehow got a picture of me and made a whole new tiktok account with the picture as his profile picture and set a insulting name that i specifically told my friends not to call me. Luckly, I was the first to find that account, and of course, i confronted him. I was not amused at all. This is not the first, not the second, but the third time. 

This guy is a horrible liar. When i asked him, he not only denyed, but he also tried to pin the blame on someone else in a group chat where that photo was sent. But it was really obvious, since i could tell by the way his messages were worded. Also, in the account's following list, his main account was the very first one. He also mentioned 2 of my accounts, and the second one, only 3 people know. however, the other 2 people would never do something like this, so i already knew it was M. I knew it was him the moment i saw that account, and he kept telling me it wasn't him. I was not playing with him and i know he was grinning behind the screen i was fucking livid 

In the end, I got the truth out of him in about 4 minutes. He kept telling me that it was just a joke and i shouldn't be so mad. But I told him so many tiimes not to post my name or pictures anywhere and i told him more than twice. 

at like, midnight, he sent me his fucking birthday wishlist and all the stuff on it was merch of my favorite character i do not want to forgive this kid oml

Should i forgive him? or should i back away for some time?