Royal and Loyal (MikaYuu)
Once upon a time, the world was ruled by the vampires, when we humans were mere servants to them.
There was kingdom called "Yolvan", ruled by a selfish king and merciful queen. They had one son whose name was Mikaela--they wanted him to be the best of all, while he wanted to live a normal life away from the responsibility of being a prince.
The fact that the king and the queen were not aware of, that their son was in love with a human slave--Yuuichiro. Mika didn't want to tell his parents about his love for Yuu, for they would be angry because he fell in love with a human slave, and above all, for them love between two males was an unforgivable sin.
P.S: I don't own the characters, they are all from Owari no Seraph manga by Takaya Kagami, accept for the king and the queen.