夫・誠に促され、一人で義父の家を訪れたあおい。そこへ3カ月のマグロ漁を終え、禁欲状態のまま帰宅した義父・良蔵が現れる。家政婦と誤解されたあおいは、飢えた良蔵の猛々しい欲望に抗えず、強引に抱かれてしまう。夫にはない野性的な逞しさと、獲れたての魚を振る舞う義父の甲斐甲斐しさに溺れるあおい。誠の不在をいいことに背徳の海に沈んだ彼女は、3カ月後、再び情欲の待つ義父の元へと迷わず足を進める。

Urged by her husband, Makoto, Aoi visits her father-in-law's house alone. There, her father-in-law, Ryōzō, returns home after a three-month tuna fishing trip, having been in a state of abstinence. Mistaken for a housekeeper, Aoi is unable to resist Ryōzō's insatiable desires and is forcibly embraced by him. Aoi is captivated by her father-in-law's wild strength, which her husband lacks, and by his attentiveness as he serves her freshly caught fish. Taking advantage of Makoto's absence, she sinks into a sea of depravity, and three months later, she returns without hesitation to her father-in-law, where her desires await her once again.