A young child that was aboard the Aegis vessel with Conan and the others. He is allergic to milk and has to take medicine for it if he drinks it, therefore he always carries pills around with him. His father named him Yuuki to be brave. He was threatened by X to act as his son aboard the Aegis vessel, so as to not make him look suspicious. If Yuuki were not to comply with his orders, X threatened to kill his father.