Fujinomiya Soujirou is transported to a fantasy world with only his Daisho (pair of samurai swords) in hand. The katana can talk and swiftly informs him that it is Hotarumaru, the legendary national treasure of Japan thought lost during World War II. The wakizashi is too young to have a voice, so Souji names it Sakura. This is the story of Souji and Hotarumaru's journey through a new world as he seeks to achieve ... a sword harem?