As a child, little Rui wanted to become a doctor and help people and innocent animals, but as he grew up, he realized that cries of pain and pleas with tears in his eyes were much more tempting than ordinary words of gratitude. Once a lifeless human body and an ordinary living dog were brought to him for experiments, after which the mad scientist decided to cut out the still beating heart of the animal and sew it to the human body. Some time passed, and suddenly Tsukasa came to life, dog genetics was quickly passed on to him, ears and a tail appeared like a dog, but his very human body and gait did not change. "Hahaha, behold my genius, I sewed it from dog hair, endowed it with consciousness, and the name of my creation is Tsukasa-kun~"