In Episode 17, he reveals he may still be slightly obsessed with you or at the least still see you romantically. In Episode 14, he reveals he can play the flute, but not the guitar, since his father thinks it's for 'delinquents' which he says is true when he sees Castiel.
In Episode 18, when Kentin goes into a classroom and finds Castiel in there, he does a 180 turn in the other direction and leaves. In Episode 13, he claims Castiel 'is a wimp' compared to himself, but when Alexy tells Kentin that Castiel is behind him, Kentin gets so scared he almost falls.
Ken at the beginning was afraid of Castiel, even if he didn't want to admit it. It is revealed by ChiNoMiko the brand of cookies he eats in the game are none other than Prince De Lu Cookies. Throughout the military experience, one of Ken's traits never changed: He still loves cookies. Ken was in the gardening club before leaving military school.