Relationships
He knows he isn't a good person. He spends enough time emulating good people to know that whatever he is, it isn't that. In the end, he's not sure it really matters, as long as he accomplishes his goals.
Touga uses people. The relationships other people form out of a desire for companionship, so they know they're not alone, whatever -- they're not for him. He has no use for something as simple as friendship in his life. Even his little sister, who he loves, is a victim of this point of view.
Life is cruel, so will he be.