Mikado Nakajima serves as the student council president at Aokisora High School. A diligent third-year, he and his friend Masamune Sakurakouji adopt a protective stance towards younger students, including Natsu Asumi. Mikado actively advises his peers, exemplified when he suggested the Liberal Arts club to Masamune Sakurakouji and intervened to caution against intimidating first-year students Towa Honda and Haruki Mishima.

Romantic feelings bind Mikado to his childhood friend, Waka Kisaki, who is also his step-sister. Their complex relationship unfolds within the school environment, where classmates encourage Waka to run in student council elections, a situation that inevitably draws Mikado into her orbit. His presidential duties encompass overseeing major school events, notably the cultural festival and the student council elections themselves.

The meaning of his name reflects his role: the surname Nakajima signifies "middle island," while his given name, Mikado, translates to "emperor," echoing his position of authority.