Weiss Kreuz (WK) is a group of assassins comprising of Aya, Youji, Ken, and Omi, who aim to eliminate various societal threats. Each member possesses a unique combat style, with Aya utilizing a katana, Youji relying on strings for strangulation, Ken using metal claws, and Omi employing an array of projectiles. The group is guided by their mysterious leader, "Persia," and undertakes missions involving issues like drug rings, terrorist factions, and more. However, they discover that all their targets are somehow linked to the influential Takatori family, one of Japan's most powerful clans. To combat the root cause, WK must confront and neutralize this formidable family.