A man with a cuckold fetish returns home with a prankster and introduces his wife to a junior colleague from work. As he is her husband's subordinate, the wife gradually opens Kokoro to him. When the prankster approaches the wife while the man is away, she refuses him, but she cannot resist the temptation of the younger man's cock and accepts it, thinking, "As long as my husband doesn't find out, I'll accept it." The husband is watching his wife from under the bed...