Havent had time 2 edit yet, sorry if my drawing looks like trash- I tried-)
Above is le normal/passive side, (skeleton form for both, human form is mostly the same apart from him having skin and his hair being switched to show the human-like eye (not the same as possessed)
(His age: 22)
Below is le possessed form, (by a chara of course) which is result of a previous incident that Im not going into- The human/chara's eye is normally covered by his hair, and only takes effect when possessed, otherwise it's just acts like a normal eye. (FYI- He can see through his hair)
Color reference in advance-
(Face accessory is not technically necessary-)