Ken-chan operates a Shinki hobby shop and holds deep technical knowledge of these small combat and assistance robots. When Kaguya, an Angel-Type Arnval Mk.2 Shinki repaired by a boy named Tsubasa, enters his shop, Ken-chan immediately identifies her as non-standard. He deduces she harbors a significant secret, likely tied to fragmented memories from past battles.

After Strarf Mk.2, Kaguya's former partner on a retrieval mission, captures her and takes her to a secret institute, Ken-chan intervenes. He informs Tsubasa and aids the boy in infiltrating the facility, driven by his understanding of Kaguya's unique nature and potential peril. During the infiltration, they discover Kaguya has entered a berserk state; Ken-chan supports Tsubasa's efforts to reach her and restore her senses.

Following the resolution of the crisis involving the large weaponized Shinki Athena, Ken-chan extends an offer of employment to Tsubasa at his hobby shop. This arrangement allows Tsubasa to stay near Kaguya and Strarf, who remains with them after the institute events. Ken-chan's role centers on facilitating the rescue mission and providing ongoing support through his shop.