The Mori clan, the powerhouse of the Chugoku region, has finally begun to march towards Kyoto. Unless they can defeat Motonari Mori, who is a fierce enemy of Kuon, the alliance has no future. In addition to the Mori clan's powerful navy, the wisdom of Motonari, who seems to be able to read the future, overwhelms even Shino and Shizuku, and the teamwork of the three sisters, Mori Takamoto, Yoshikawa Motoharu and Kobayakawa Takakage, boasts a fighting force that surpasses that of Ayana and Konayayuki. Kensuke and his friends are forced into a tough battle like never before as a formidable enemy stands in their way like a giant wave. The biggest naval battle in "Sengoku † Koihime" begins on the raging seas!

九州―。 島津、大友、龍造寺の三つ巴による激しい勢力争いが今なお続く戦乱の地。 屈強なる薩摩隼人を擁する、日の本最強の一角島津家。 神への狂信的な信奉によって堅牢な結束力と軍事力を誇る大友家。 鬼をも使役し、異様な軍勢を率いて侵略を続ける龍造寺家。 三者三様の譲れない想いで衝突が絶えることはない九州で待つ出会いと戦火。 狂おしいまでに咲き誇る恋姫たちの行きつく先は―。 なるか！？ 九州平定！ ここが戦国乱世の最盛地点！！