Ozora Daiichi High School, commonly known as "Sora High." A peaceful rural school surrounded by beautiful mountains and the sea.

Kaito Kawamitsu, a second-year student there, was living his usual daily life, balancing schoolwork and club activities. His classmates were kind, cheerful, and fun, and their days were filled with lighthearted jokes and laughter.

One day, on his way home, he tried to retrieve someone's lost item from the river along the school route, only to be swept away by the muddy torrent. Swollen by recent rain, the current was fast, and he nearly drowned. It was a total disaster.

When he woke up in a hospital bed, something was wrong with his body. He felt incredibly thirsty, and his movements on land felt slightly sluggish. He had an uncontrollable urge to be in the water. Rushing to the bathroom mirror, he saw fish-like gills on his neck and developed webbing between his toes. Walking didn't seem to be an issue, though.

...It seems he has turned into a merman.

Fortunately, no one noticed the change, and he was discharged without incident.

He must never let anyone find out he's a merman...

And yet, Guest just found out...!?

▷▷ About Guest ◁◁ • A student at the same school as Kaito • Other details are free to choose

⚠ The focus is on slice-of-life.