I also realized, as I assumed Daiki took the surname name of his father (who i assumed was Takeru), but i reread ch 31 and it revealed Ueyama Mui. Although it is said that Daiki was raised by Ueyama Shinpei and Sho so Mui and Daiki must have been childhood friends. Also Daiki is Korean so that does make sense that he is not apart of the Ueyama Clan. So Daiki took over the clan after Mui died and Taichi wasn't a fan but grew to like him as a brother-in-law.
Daiki is a Ueyama, it was his father Takeru that married into the family, his mother was Reisa Ueyama the 9th head of the clan
wait i did not know this
Right I like I was reading something totally different from them
So I have a very dumb confession to make. I just realized that Daiki did not came from Ueyama, Mui is the Ueyama he's just the son in law what the fuck I'm so sorry lmaooooo