The series is about a girl named Momo who attends high school at the city of Sorasaki. However, she is secretly a member of Tsukikage, an intelligence agency that protects people. As a new member of the agency, she works alongside her colleagues including her senior Yuki and friends. Together, they work to establish peace in the city.

All Momo wants is Yuki’s approval, but her mistakes nearly botch Tsukikage’s missions! Is she really cut out for this role or will experience come with time?

As an apprentice, Fu owes a lot to Tsukikage, especially to Mei. How far is Fu willing push herself and what can Mei do about it?

Momo’s dedication to the cause negatively impacts her personal life. Meanwhile, the Moryo organization establishes a new affiliate to lure Tsukikage out into the open.

Humanity can be cruel. Two friends were torn apart and forced down divergent paths. One joined Tsukikage, and the other joined Moryo. What happens when they reunite?

Theresia continues her investigation into Hatsume’s ties to Tsukikage. Hatsume attempts to rekindle her old friendship with the Moryo agent but where will this leave Goe?

Tsukikage travels to Okinawa and discovers that their contact, The Shisa, have been wiped out by the Nirai Kanai. Meanwhile, Goe bonds with a girl claiming to be a Viking.

All members of Tsukikage had mentors at some point. Yuki tells Momo the story of her own mentor, a girl known as Nagaho. Whatever happened to her?

All things must end, and that includes Moryo's reign of terror. The countdown begins while Tsukikage has a heart-to-heart. They prepare to take down Moryo once and for all.

It was a trap! With the traitor revealed and Tsukikage decimated, Moryo’s ambitions now stand unopposed. However, it is always the darkest before the dawn...

Project Gekkako is now up and running. With only a few remaining members of Tsukikage left, will they be able to save everyone or fail as others before them?