Reimu Hakurei is the Hakurei shrine maiden. However, in this world of eternal summer, it seems she's known as the Leisurely Shrine Maiden of Paradise. She doesn't attempt to gather worshippers, nor does she clean the shrine grounds. The reason is simple: Hakurei Shrine has sunk to the bottom of the ocean.

This world's Hakurei shrine maidens are known as Beach Shrine Maidens. For generations, they watched as Hakurei Shrine slowly sunk beneath the waves. Under Reimu's watch, the shrine became fully submerged, vanishing from sight. Faced toward the sun as it rose above the horizon, toward the place where Hakurei Shrine once stood, Reimu put her hands together in silent prayer.

A swarm of butterflies were gently flapping their wings above the sand. It was a rare sight. As Reimu approached the butterflies, she spotted something on the ground. "So this is why you're here," she said as she picked up a tropical flower that had washed ashore. She had no clue how much pollen had been claimed by the sea nor how precious that pollen would've been to the butterflies. Once more, the butterflies approached the flower. Captivated by their fluttering wings, Reimu failed to notice the wave crashing toward her. "Eep!" Reimu let out a quiet squeal of surprise as she fell back onto the sand.

Reimu was now lying on the beach, watching the butterflies dance this way and that. She let go of the flower and slid herself down the beach. The sand beneath her fell away as the water deepened. A world made of nothing but sea and sky. Oh, and butterflies. Suddenly, Reimu dove under the waves. The water blurred her vision as she looked up beyond the surface. The butterflies' dance appeared even more erratic than before. It's said butterflies are a symbol for the soul, and gazing up at them, Reimu thought they truly looked like fluttering souls―souls that couldn't resist the pull of a lone tropical flower.

That's when Reimu realized. She was seeing the world from the perspective of the now-sunken Hakurei Shrine. With her ability to fly, she must seem just like those butterflies in the shrine's eyes. The instant that dawned on her, she burst up from beneath the surface. The idle young maiden now danced on the tidal breeze with the butterflies and flowers. "That's right. I should be able to fly freely. Fly to anywhere I choose. The sky is freedom!" exclaimed Reimu. From the beach, a voice called out to her. It seems the swimsuit she'd requested was finished. "With that, I might be able to fly through the water as well," she thought to herself. How far does this world's sky stretch? As far as she wants it to. Such is the freedom that was given to her.