Ikeda Hisoka and her twin sister, Ikeda Akira are both former assassins. They have gotten their hands stained, but, they want to get rid of that past. The two have hidden their assassin identities, and started acting more like normal teenage girls. They had enrolled in an elite school in Japan, Kunugigaoka Junior High. Hisoka, the quiet one of the two, landed in the top class. Though she was never happy. After a small encounter, she ended up getting transferred to the end class. Now, everything is finally changing for her.