hair originally black and eyes were green then his hair turned into a mix of black and silver and his eyes were green on the left and icy blue on the right after making the pact to Yukihime
he is 5 foot 11 inches
personality seemingly cold but caring as well as very protective of his friends
Yukihime personality sarcastic caring
Shinji was born in a shrine temple in the mountains where he lived peacefully until one night when he was 7 when it was attacked by a group of people. He know not who they were just that one man said that the light needs a new host. So when he was told to run he ran until he stumbled upon a cave with-in it was a sword that gave off a cold air and as he grabbed it it asked him what he would sacrifice for power at the time he said nothing and just ran back to see if he could get it to someone. When he got back he found the temple burned and everyone dead or missing. Thats when he was asked once again what he will give for power only this time he saw an image of a dragon with bright silver scales and icy blue eyes. He asked if he makes this pact if he would be able avenge his family when she said yes he offered his heart where it changed his heart to one of a demon causing his blood to be mixed. He spends 9 year training in the forest with the animals as Yukihime teaches him about demons and survival. When he is one day visited by Mephisto asking if he was interested in learning more and being an exorcist with Shinji asking if he can help search for the people who killed his family. Where he moves into a rundown dorm and meet the Okumura brothers.
the Demon sword of White Flames: Yukianesa said to have sealed with in is the silver dragon Yukihime whos white flames froze all it touched
with the blade sheathed Shinji has control over ice but when the blade is drawn he is covered by white flames but he can only use them for so long before his body starts to break down as it is still human.
uses his ice power on the ghoul during the blackout exam where he explains how afterwards
feel free to change thing this is just a rough idea i got in the middle of the night though the sword and the pact stays the same