Why is this guy suddenly taking interest?

I know him through a mutual friend and we chat on the same platform together with a few other people. He suddenly started commenting on things I said within the group chat, then he suddenly started chatting to me, which led him to relentlessly teasing me. I do not mind because I do the same thing back to him. Now everytime I start chatting on there he always starts teasing me all the time.

It has gotten to the point where everyone on the group chat have started to pair us together as a couple, and calling us "newly weds". He doesn't react to it though, but I have a good laugh.

I started playing a game with another friend from the group and we group voice call (anyone from the group chat can join in), and I have seen him come into the call more than 5 times whenever me and my other friend play it, he does not say anything he just listens to what we say and do

I ended up inviting him to play, which he bought and now is waiting for me to play it with him.

He always finds ways to tease me relentlessly, does not matter what I say. It makes me laugh but he does not do that with other girls in the group chat. He teases them mildly, but not as strongly and repetitively as me. He purposely seeks out to tease me!

Why does he do this?

Why is this guy suddenly taking interest?
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