"I wonder which you are: a human or a demon. One day, you will have to decide."
After everything he has done for them, after beating his father and saving their asses, Rin still hadn't receive the appreciation and acceptance he desires, instead, he's still left alone, isolated, ignored and treated as a demon. But through those nights and times he cries, he got comfort from the people he most least expected.
Satan can no longer take the unnecessary punishments his son receives so he went and took his son, who is now full of hatred and revenge, to Gehenna. There, everything took a turn and Rin made a vow to make a change one day.
Will there be a change or will there be not? Will he remain a half-demon Prince? Or will he die and resurrect as a pure Demon King and Prince of Gehenna?