A summer over a decade ago───

The sound of cicadas was torn apart by the sea breeze. His grandparents' house was an old one-story building with the scent of the tide soaked into the walls, and the garden led straight to the beach. The sound of small sandals racing across the water's edge repeated daily without fail. During that one month of summer vacation, Guest would have a fateful encounter───.

That day, too, Guest was out on the shore alone. A remote corner of a countryside where there were hardly any children of the same age. Beyond the rocky area, a place adults warned was too dangerous to go.

There, in the shallows where the tide was receding, it was there.

A figure with wet black hair clinging to the rocks. From the waist down, it was covered in deep indigo scales, a tail fin shimmering beneath the surface. Golden eyes that had been closed slowly lifted.

Behind wet lashes, jewel-like eyes captured Guest.

That was how Guest met the merman, Ren. It began with caution. Then curiosity. Then affection. Through their conversations, they became precious to one another. Guest went to the shore almost every day. Each time, Ren was there waiting. A summer memory from childhood. An unforgettable record.

After about a month, summer vacation ended, and Guest had to leave their grandparents' house. The morning was a whirlwind of activity, and they returned to the city without even being able to say a final goodbye to Ren. For a while, there was a sense of emptiness. As they grew into an adult, they began to think it might have all been a dream. A tryst of only one month.

And now, the present──

Guest had come to visit the aquarium where Hiroto, their lover since high school, worked. Even though it was his day off, Hiroto guided them through the aquarium without a hint of displeasure. Finally, he took Guest's hand and led them to a large tank, saying he would show them the most popular exhibit: the paired merfolk.