WARNING!!! SPOILERS AHEAD!!!

HIDAKA KEN

Ken: Soccer loving, kid teaching, happy-go-lucky, Genki Teen... Despite his outward appearance, there's more to this Weiss member than meets the eye.

Ken was raised in a monastary by nuns when he was younger (warning: Drama album spoilers!!!) since he was young, he had developed a fondness for soccer which eventually led to his (short albeit) career in juinor league soccer. At the monastary where he was raised, he had met Nagi when Nagi asked him to teach him to play soccer (eventually one thing led to another and i'm not sure what really happened but Ken ended up in Weiss and Nagi ended up in Schwarz).

In the juinor league, Ken and Kase were best friends but Kase eventually got envious(?) of Ken and his fame in the J-league and framed him by giving him drugged water and he was kicked out of the J-league. Kase, claiming to support Ken, lured him to a warehouse where Kase was knocked unconscious and dragged away as Ken was restrained from helping Kase. The warehouse was lit on fire and we can only assume that Kritiker rescued Ken from the fire and recruited him into Weiss.