Keiko, an insurance saleswoman, visits a client one day and is asked for sex instead of a contract. The man explains that his parents can arrange a major policy, but only under the condition that she participates in BDSM play. The parents, Arisue and Chiaki, impose strict terms within the agreement, pushing Keiko to test her own limits. Under the guise of a contract, she becomes bound and entangled in a new, twisted relationship.