//I don't know an awful lot of this subject either and this just what I saw on tumblr and TikTok so I'm trying-

You one day wake up with a little red string attached to your pinky. So naturally you get up to go find who it's connected to. But it was Katsuki Bakugo. You two didn't get along all the well. So neither of you were all that please to hear your 'soulmates.'