I'm starting to assume he's just an original character. I think it was supposed to be the mock turtle. He represents my boyfriend :) not fair. You already got lee joon, mir, and luhan. In the manga, arisu slammed the door on tatta so hard that his entire hand just came off.
Tatta is a giant red herring for no apparent reason. Why did the show creators/ wardrobe do this:
Musk S Space X Launches New Tender Offer For Shares