Season 1

A sudden accident shatters the everyday happiness two couples had always taken for granted — and exposes a secret one of them kept hidden for years.

Itsuki reveals he saw Azusa and Mitsuru together on "the third Friday." Sakiko wants to believe her husband, but begins investigating their secret.

As their investigation stalls, Sakiko and Itsuki bond over shared frustration. A call from the police leads them to retrace Mitsuru and Azusa's steps.

The discovery of two sets of tickets forces Sakiko and Itsuki to confront the possibility of an affair. Sakiko then finds a new clue on Mitsuru's phone.

A year after the accident, Sakiko and Jitsuo have forgiven each other. One day, a student who was at the scene of the accident with flowers in his hand met a certain person.

Mitsu returns home, and Sakiko recalls the first time she meets Mitsuru and the days she spent as a couple. Sakiko and Jitsuo hear the story from Mitsuru.