When Suzu's beloved older sister figure Mao disappeared, Suzu was summoned home to take over as Tamayori-hime — the miko destined to sacrifice herself to protect the land from the wrath of the sea lord. She knows only that the role comes with a small group of retainers; almost everything else about it is a mystery she was hoping to untangle by finding Mao first. Before she can adjust, the sea lord attacks and sends demons into the village. The head of the demon forces is Mao.