In order to exterminate the demons that have spread throughout Hinomoto, the Hinomoto Alliance has united the forces of powerful daimyo under the banner of Nitta Kensuke, a celestial being who has been transported from the modern era. To fight the ongoing damage caused by demons in various places, they aimed to further expand their allied forces. While Oda Nobunaga and his men were enjoying a brief period of peace, they received news from Satake Yoshishige in the Tohoku region that Date Masamune had turned into a demon and was attacking Hitachi. What awaits them in the Tohoku region?

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!