Kiri Ito is a 25-year-old office worker who has spent three years in a company enduring a life of quiet desperation. Her days are a relentless grind through a pile of energy drinks and exhausting work, compounded by sexual harassment in the workplace and a boyfriend who subjects her to moral harassment. Her only guiding philosophy has been a simple desire to be useful to other people, a value she clings to in order to survive her daily existence. This life of total dedication reaches its breaking point when a mysterious letter arrives in her mail. Inside is a single card, and this card grants her the right to live freely. The arrival of this card marks the end of her selfless devotion and signals the beginning of a final, great revenge that she decides to enact upon those who have wronged her.