Special episode introducing a new character.

In Japan, betting on horse racing is one of the few legal forms of gambling; thus, the public races have become an interesting part of Japanese culture. In this sport, an individual who rides a horse and competes in races is called a jockey—that is just what Yuu Arimura aspires to be. Becoming inspired after witnessing a derby, 15-year-old idol Yuu shocks the entire nation when he leaves the entertainment industry to enroll in a prestigious horse racing school. Excited to pursue his latest passion, he gradually bonds with his new classmates—such as the talented Shun Kazanami and the self-assured Amane Grace—who are each unique in their own way. Although the path ahead may be full of obstacles, Yuu is determined to pursue his ultimate goal of becoming one with his horse.

A hundred years after catastrophic shifts in tectonic plates caused most of its area to submerge, Japan now thrives as a maritime nation. High functioning cities line the coasts of Japan, and well developed sea routes are defended by specialized naval ships. The marine industry is flourishing, and young girls are eager to join the Blue Mermaids—highly skilled women who devote their lives to protecting the seas. After some time apart, childhood friends Akeno Misaki and Moeka China are reunited at Yokosuka Girls' Marine High School. Here they are joined by others who share their dream of becoming Blue Mermaids. Soon, training exercises commence, with Akeno and Moeka being put in charge of their own ships and crew. Everything is progressing smoothly for Akeno as she settles into her role as captain and builds camaraderie between her fellow crew members aboard the Harekaze, a destroyer ship. However, unexpected engine and navigation failures soon leave their ship stranded and the crew in danger. High School Fleet follows the Harekaze's valiant crew as they navigate treacherous waters and other obstacles on their quest to become fully fledged Blue Mermaids.

The energetic Tapio Chatarozawa and the cool-headed Kuehiko Roshihara are two young cats trying out various part-time jobs. From delivering packages to washing windows on skyscrapers, the pair explore the opportunities that await them out on the recruiting field. As they struggle to learn the ropes, the duo endures the antics of their colorful customers and supervisors while bonding as working buddies.