Riku Miyagusuku (宮城リク)

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.


Draining Riku's blood seems to cause Diva to develop a strong interest in him. She takes Karl to the Red Shield headquarters to find Riku. Once she finds him, she rapes him and then kills him with her blood. In the light novel adaptation, it's explained that something in Diva's eyes causes the Chevalier blood in Riku to react with a "maddening desire" that causes him to be incapable of escaping or physically resisting Diva's actions.
After Riku's death, Kai has a piece of his crystallized body made into a pendant, which he wears around his neck to remember his lost brother.