Reimu Hakurei is a beach shrine maiden in the world of eternal summer. Each morning, she offers a prayer to Hakurei Shrine, which has sunk beneath the waves. Reimu likes battles in every world, but this Reimu has taken it a step further. She enjoys all kinds of competitions, and she hates losing. She goes around challenging random people by throwing her yin-yang beach ball at them.

Sanae Kochiya is a living god in the world of eternal summer. For some reason, standing before the ocean has a liberating effect on people. It can sometimes help to take a walk along the beach if you want to ask for advice or open up about something. This Sanae is more honest with herself, and she unashamedly loves to play. Lately, she's been thoroughly enjoying digging for clams.

Amid the lapping waves and songs of sea birds, the palm trees swayed in the gentle ocean breeze. Taking a deep breath of this refreshing air would make anyone excited to play. Such was the case with Sanae when she arrived at the beach with a bucket and spade in hand. She had only just started to wade through the shallow water as if in search of buried treasure when she got soaked by a big splash behind her.

"Oh, there you are, Sanae. I've been looking everywhere for you!" After Reimu surprised Sanae by splashing her with water, she casually walked up to her, tossing her beach ball from hand to hand. "What are you doing?! You're gonna scare the clams away!" "Clams? Who cares about clams? C'mon, I challenge you to a rematch!" Before she had even finished talking, she tossed the ball up into the air and slammed it down at Sanae. It seems she was still angry at losing to Sanae the other day. Sanae instinctually knew that there'd be no escaping the battle if she received Reimu's serve, but she didn't hesitate. "You're on!"

Sanae gracefully hit the beach ball, causing it to arc high up in the sky like a second sun. But Reimu was ready, and she received it, setting up for another attack. Even though the water was up past their knees, it barely hindered their movement as the heated rally continued. "It doesn't matter how cool and stylish your swimsuit is, I'm not gonna lose to you!" So saying, Reimu put all her might into a viscous spike directed right at Sanae. "Really? You think I look cool?" As Sanae lifted her hand to her mouth to try and hide her glee, her elbow miraculously hit the ball, launching it on a curving trajectory to splash into the water next to the stunned Reimu. "Oh? Did I just win?" Reimu begrudgingly accepted the loss and spent the rest of the day helping Sanae dig for clams.