A Japanese Spriggan agent stationed in Japan. He is extremely young and is the protagonist in the manga and in the OVA.

A slacker at heart, Yuu is the typical delinquent who happens to get in trouble with some of his teachers since he doesn't pay attention to some of his classes. In addition, he cuts classes for most of the time, leading to teasing from his peers to think that Yuu wants to avoid school since these are only good times for him to conduct his Spriggan missions in secret before he graduated from high school . At one point, Yuu wishes that he wasn't a Spriggan agent, but he doesn't regret where he was now. Despite his high school lifestyle, Yuu is an expert in martial arts, firearms and commando tactics, thanks to his years of indoctrination with COSMOS and his military training with ARCAM. Yu can defend himself easily from all known threats.