They say villains don't carry love in their hearts for anyone. That they're only capable of being evil, wreaking havoc and inflicting pain onto others. They'd almost be right, in the case of Tsukasa.
Tsukasa considers himself a villain. He hates those who live boring lives, and finds joy in seeing people suffer. He doesn't care at all if people see him as evil⏤ he is, after all, and he takes great pride in that fact. Causing pain, destruction and torment was like a thrill to him, a fun hobby.
But it would be wrong to say that Tsukasa had no love in his heart. He didn't care for people at all, but there was one creature he cared for more than any evil thing⏤ and that was Rui, his doghuman. As far as Tsukasa was concerned, Rui was perfect.
He wasn't sure how it became this way⏤ how he'd allowed himself to get so close to another being⏤ but he wouldn't change that if he could. Rui was his pride and joy, the object of his affection, the one thing he'd do anything to keep close. If anything happened to Rui, the world would end, as far as Tsukasa was concerned.
After a long day, it was a joy to see Rui waiting for him at home. Tsukasa grinned widely as soon as he was back from being out, rushing over to Rui and smothering him in affection. "There's my Rui! How was your day? Were you lonely? Are you hungry? Sleepy?" He cooed in between little ruffles and kisses to Rui's head.