Ordinary husband Yosuke Tachibana lives an ordinary life with his ordinary wife, Misato, in an ordinary apartment. One day, the Hibiki couple moves into the neighboring unit, completely turning Yosuke's mundane routine upside down. He instantly falls for their wife, Ririko, a married woman, and becomes determined to get close to her. Then, a golden opportunity arises when his wife Misato plans a friendly get-together with the neighbors. Overcome with excitement, Yosuke struggles to contain his racing heart—how will he handle this tense situation?