Master spy of the Imperial Army and founder of the spy training program "Institution D". Has the nickname "Demon Lord", he has a brain that knows no limits. Used to work as a very efficient spy himself. The trademark white gloves and cane are rumored to be a result of being captured while in an enemy country because of an ally's betrayal and then tortured, but the details are unknown. Friend or foe, many try to find out his true nature, but every attempt to do so has always ended up in failure.

Lieutenant of the Imperial Japanese Army. Under orders of his superior Colonel Muto, he heads to Institution D that was secretly set up within the army. Acts as liaison between them and the staff headquarters. While surveying the members of Institution D, he is amazed at their abilities that go beyond common sense. Like a militia, he has a sincere personality, and often is angered at the lack of modesty in statements from Miyoshi and company.

Narcissist who always treats others with a sneering attitude and looks down on them. Has the habit of putting on an air, such as taking very gallant poses. Sometimes offers to manage the institution members along with Kaminaga.

A mischievous playboy that seems frivolous, but actually is full of pride, and always makes sure to accomplish anything he says. Like Miyoshi, sometimes offers to manage the institution members.

An Institution D member that stands out as he went to the Army's elementary school and military academy and was appointed as second lieutenant in the past. Reticent, and almost never laughs. There is some other secret on top of his past different from others, and harbors a wall of some sort between himself and the other members.

Oldest among the institution members along with Kaminaga. Sociable personality and good at taking care of others, he is the big brotherly figure of the institution. Has the disposition of a freeman, and doesn't care much about details. Used to handling women.

Smallest member of Institution D. Charming but full of pride. Has a cheeky personality. Agile master of martial arts.

Unpretentious, and often worried about Sakuma who lived together with Institution D members after he was sent in from staff headquarters. Androgynous and usually gentle, but shows a sadistic coldness on occasion against enemies.

Tallest of the Institution D members. Slightly airheaded, sometimes can be found spacing out. Reticent, doesn't show much emotion. Seems to get along with silent Odagiri. Likes to cook, and sometimes cooks for the institution members.

Gentle-mannered, pleasant young man with an intelligent aura. Often seen as older than his actual age as he always is calm. Has the habit of performing magic unconsciously with items near him when he is in thought.

Often worries about appearance, but the personality of this pleasant young man is down-to-earth and is very faithful to his missions. His skills at chess are as good as a professional player.

Colonel of the Imperial Japanese Army. Has unpleasant feelings towards Institution D led by Lieutenant Colonel Yuki.