OKAY LISTEN SO HERE'S MY THING, I truly think that he's a burnt out Gryffindor, baby Kei was all Gryff and a lot of his story arc (THIRD YEAR CAPTAINCY ARC???? @GOD PLEASE) is him finding!! that pride again!!! and while he slots in really well with both Slytherin and Ravenclaw characteristics, I think that ultimately, he grows best in the midst of Gryffs, and that's a Hat consideration. Because while everything about these house values might annoy him, it's what ultimately moves him forward and lets him find himself.

The courage to believe in others again, a fire lit under his ass. Kei doesn't want to admit it, but he's a stupid lion just like the rest of them.