Natori Keiko (Yoshitani Ayako) originally lived a happy married life as a stay-at-home housewife. One night, she accidentally looked at her husband Shinichi's (Seto Toshiki) cell phone and began to suspect that he was having an affair with her friend Yuka (Murase Sae)..But in fact, Shinichi's affair partner was not Yuka.That night, the person who had repeated trysts with Shinichi was Shiho (Rina Asakawa), Keiko's sister whom Keiko completely trusted unconditionally.

“My happiness is to see my sister in misfortune”——.Shiho has been disgusted with the top student Keiko since he was a child.She wanted to destroy her sister's perfect smile, and because of this, she took away all the important things from Keiko.However, only Shinichi is the one she seriously likes...

I haven't done anything yet, and I watched the marriage between Shinichi and Keiko just to push Keiko down from the peak of happiness...!

Keiko had no idea about this and completely believed in her sister Shiho's fabrication of an unfaithful relationship between Shinichi and Yuka. She believed it to be true and questioned the innocent Yuka...

Then as Shiho expected, Keiko lost her most important friend——!

In order to see the hurt look of the sister I hate the most... I fell from the peak of happiness! The poisonous fangs of the sister who went off the rails attacked Keiko!!