SOMEONE SPOIL IT FOR ME, WHOS HIS EX?!

Apparently the ex is jaeha(?), the blondie from another group
https://tkor059.com/%EB%AA%A8%EB%85%B8%ED%81%AC%EB%A1%AC-%EB%A3%A8%EB%A8%B8

Oh yeah it's him I read the raws, he appears on chapter 18 yikes