Beautiful mother Miyabi lives with her adult son while her husband is away on a long overseas assignment. One day, her son’s adult best friend Kento comes over to go birdwatching. Kento has carried feelings for Miyabi since childhood and suddenly steals a kiss. Her heart races despite her better judgment, and when he approaches her again and takes her lips once more, the forbidden desire she has suppressed for so long finally catches fire, drawing her into illicit kisses and creampie sex.