Taiyo Asano has been on his own ever since his parents died. The only one who seems to care for him is his childhood friend and classmate, Mutsumi Yozakura. But Mutsumi has a secret--she is the head of a family of spies!

Tsubomi Yozakura comes to Taiyo in his dreams, asking him to kill her! She tells him that in order to do so, he'll need two things. Following her instructions, Taiyo decides to take on the silver-rank spy advancement exam. Unfortunately for him, the test proctors are all Yozakura siblings...!