Reiko lives in an apartment with a couple. Her husband is a lukewarm man, and she is always frustrated with him. One night, Reiko's stepson, who is interested in Reiko's fascinating body, sees her masturbating and ask her to perform fellatio on him. The next day, her stepson- fucks her, and she wakes up as a woman. After that, she and her son-in-law have a very intense sex.