Name: YN Nagai
Quirk: Black Ghost
YN is immortal. If he dies, all of his wounds will heal and he'll come back to life within thirty seconds. If he loses a body part, and it's close enough, it will just be pulled towards him and reattach itself. If it's too far away, or can't reach YN, then it will just grow back instead.
YN also has a "paralyzing scream". He can yell and it will temporarily cause everyone around him to freeze up, unable to move for up to fifteen seconds.
Finally, YN can summon a "Black Ghost". It is invisible to everyone except him, but it can sometimes be seen by someone who is feeling extreme fear or anger. It has incredible speed and strength, and will only disappear if YN is killed or dematerializes it. It can't speak on its own, but it can repeat words spoken by YN. He calls it Joker.
If you still don't get how the Black Ghost works, think of a stand from JoJo. Or just look up Ajin: Demi-Human, it's great.
Best Friend / Love interest: Mika Shimomura
Quirk: Aerokinesis
Mika can control air. She can use it to fly, push things back or pull things towards her, or solidify air to create objects. When she makes an object, the air takes on a foggy appearance, so you can see what she's created. Mika can also feel air currents, so she can sense movement around her.
Those are the main characters! I don't own My Hero Academia, Ajin: Demi-Human, or the art used in this story! ENJOY!