Demon X Human (Riren)
Levi is the King of all demons, he is looking for his mate Eren Jaeger. He had been told that the ocean green eyed boy would be assigned as his mate since the day he was born.
Eren is raised by his mom and dad in a small home, but one night, he is attacked by demons. His father is a demon hunter and tries to kill them off while his wife and son got away, but they couldn't get far enough as they were both caught. Eren watched as his mother was slaughtered In Front of him, his father stood just a few meters away, growing angry. He was angry that Eren wasn't able to save his loving wife, so with that anger, he used it to hurt Eren to 'punish him.'
As Levi grew up, he was raised by his uncle Kenny who tortured him into depression to make him a dark evil demon, but the only people that were able to make him happy were Isabel and Farlan, but one night Kenny goes on a rampage and killed Levi's two best friends, more like siblings. As he watched this happen, he grew angry and his demon king powers full awakened and he killed Kenny in front of the whole kingdom. The only people he had left in his life were Erwin Smith, Hanji Zoë and Mike Zacharias.
As days grew older, Eren and Levi finally met, but not on good conditions. Eren was in the middle of an alleyway covered in blood, his father stood above him. Grisha ran as he saw the Demon King, but the Demon king couldn't care less, all he cared about was that he found his turquoise eyed mate, was just laying there, crying covered in blood.
When Levi saves him, Eren is first scared and doesn't know what to do, he was alone until he see a certain group he hadn't seen in six years.