Riku is the adopted brother of Kai and Saya, the youngest of George Miyagusuku's three adopted children. He is a very kind and intelligent boy who loves to cook. His gentle nature even rubs off on the reclusive Hagi to some degree, particularly after he brings Hagi a plate of food and asks him to join the others. Hagi teaches Riku how to play the cello and protects him from a bad injury after Riku falls from a moving train.