In Amawakuni, Arata, a young member of a prestigious family, looks forward to forging his own destiny until word comes that the princess is gravely ill. Unbeknownst to him, his grandmother had him registered as female at birth, and as the Hime clan, which follows matriarchal traditions, has no other female heirs, he is now next in line for the throne. While posing as a woman and waiting for a replacement, Arata witnesses an assassination attempt on the princess by her bodyguards, the 12 Shinsho. Framed for the attack, he escapes into the Kando forest, a place said to alter those who enter it.
Meanwhile, in modern-day Japan, Arata Hinohara is trying to avoid his bullying classmates. He follows a mysterious voice calling his name down an alley and inadvertently swaps places with the Arata from Amawakuni. Awakening as a Sho, a warrior skilled in using Hayagami, divine weapons, and supported by allies he encounters, Hinohara sets out to restore order to this new world.