Hidden from his friends is his Kureshima background where he was forced to live in an environment with a heavy burden from his brother, who wants him to exceed in life, likewise the same from his father, Amagi Kureshima. Mitsuzane eventually joins his brother's goal of trying to save humanity from the Helheim Invasion through Project Ark, but when his brother allies himself with Kouta, he becomes a victim of a coup d'état causing Mitsuzane to blame Kouta for his brother's "death" and causing his crush, Mai Takatsukasa to lash out at him. Through Kouta and Mai's "death", Mitsuzane is unable to see his other friends eye to eye and views himself as someone who is incapable of their friendship.