Legends tell of immortality bestowed upon those who consume mermaid flesh, a fate embraced by Yuta and Mana. Their eternal lives lead them on a quest across diverse lands in search of purpose or a possible remedy. Along their journey, they encounter Masato, a fearful child entangled in a peculiar bond with his mother, Misa. As Yuta and Mana delve into the unsettling mystery shrouding Masato and Misa, they also face the enigmatic emergence of monstrous entities. What secrets will they unearth, and how will their encounters with these otherworldly beings shape their fates?