Two years ago, he was one of the best Demon Slayers in the world. Ryuzu even had a trophy in his honor after he had slain a demon sent on destroying the Bunny Planet. However, two years later, Ryuzu got lazy with his job and was fired. Many of the students trash Ryuzu, much to the annoyance of Oishi. His current job was supposed to be protecting the Kitten Planet, but his negligence has caused the planet's complete destruction. Ryuzu Kawaii is the father of Oishi Kawaii