The Right Arm of The Saint I: 300km south of Tokyo is a man-made island, Itogami. Akatsuki Kojou, a high school student at Saikai Academy is on his way home when he notices a girl in Saikai Academy middle school uniform following him.
(The Right Arm of The Saint II) Yukina moves into the room next to Kojou's. Kojou takes her to a shopping mall to buy home essentials. His sister Nagisa cooks a welcome dinner for Yukina. Later, there's a destructive attack nearby.
(The Right Arm of The Saint III) In the battle last night, Yukina was shocked to see how vastly Kojou's power exceeded that of Familiar. Kojou and Yukina locate the escaped Eustach to a lab, where another intense battle awaits them.