When an evil emperor executes their leader, his band of knights – bound by duty and honour – embarks on a journey of vengeance that will not come to an end until they've destroyed their mortal foe.

Ruka is a young girl whose parents are separated and whose father works in an aquarium. When two boys, Umi and Sora, who were raised in the sea by dugongs, are brought to the aquarium, Ruka feels drawn to them and begins to realize that she has the same sort of supernatural connection to the ocean that they do. Umi and Sora's special power seems to be connected to strange events that have been occurring more and more frequently, such as the appearance of sea creatures far from their home territory and the disappearance of aquarium animals around the world. However, the exact nature of the boys' power and of the abnormal events is unknown, and Ruka gets drawn into investigating the mystery that surrounds her new friends.

The movie starts off after the events of Episode 3, when Kisaragi had sunk. The Mikawa Fleet (Furutaka, Aoba, Kako, Kinugasa and Tenryuu) are in the middle of Night Battle. Choukai uses Searchlight and gets medium damage, but they win in the end. A New Fleet Girl gets "dropped", emerging from the sea. It is Kisaragi. Kisaragi is brought back to the temporary base in Solomon Islands, but she is suffering from PTSD and has amnesia, unable to remember anyone from back in the anime, excluding Mutsuki...

Kotaro visits Komada Distillery for a project on Japanese craft whisky. Led by young female president Rui, who took over the family business, the distillery works hard to reproduce its signature whisky, Koma, which they had to stop making years ago. However, not to mention financial backing, too many clues are missing to revive the once lost whisky.

Part one of Toku: Touken Ranbu: Hanamaru ~Setsugetsuka~