Hitotsubashi Kiriko is sinking into a pit of sorrow when her one and only best friend whom she lived with for three years, dies of illness. Living on a pension and working part-time is not easy, and the thought of having solitary death terrifies her.

One day, she was fascinated by the statement of an arrested person she saw on TV which inspires her to commit crime so she could live in prison. And so, Kiriko's "Life in Prison" plan began. As Kiriko proceeds with her crime plan, she finds new experiences and encounters.