Having passed the tryouts (selection exams), rookie recruits Akira, Will, Ren, and Gast proudly become HELIOS's 13th generation of Heroes. They attend the entrance ceremony with their own thoughts in mind. However, the stage for the Heroes' festive entrance ceremony is also a golden opportunity for Siams and Shin of Eclipse, who are after Substance, to set their sights on HELIOS. Eclipse appears before the HELIOS Heroes in a huge explosion. Thanks to the efforts of Akira and Will's mentors, Brad and Oscar, they manage to defeat Eclipse and avoid disaster. Meanwhile, Akira, who didn't perform as well as he'd hoped, seems to vent his frustration by boasting that he'll make South Sector, where he's been assigned, number one in LOM (League of Millions), a ranking competition for Heroes. Akira and the others are excited about being able to act as heroes, but Eclipse, operating in secret, is plotting to steal the Substance from HELIOS...

[HELIOS] It's been a while since the 13th training team began... The North Sector, which boasted an undisputed No. 1 ranking in the [Sector Rankings], finds itself in an unexpected predicament. Marion, the youngest mentor in history, is deeply hurt by North's drop in ranking, and is unable to control his emotions, becoming frustrated. The other mentor, Victor, is only interested in researching [Substance]. While rookie Gast struggles to rebuild the team, fellow rookie Ren is obsessed with revenge against [Eclipse], who killed his sister and parents. The team is far from united. As if reflecting the team's fragmented situation, the city's security deteriorates, and trouble breaks out one after another. To make matters worse, an [Eclipse] entity known as "Zero" begins appearing in the North as well...

New Million, "the city where a million dreams come true," has developed thanks to the efforts of its Heroes. In this city, visited by people from all over the world, a dome-shaped stadium floating on the sea has been born. It's called "Grand Sea New Million." Plans to hold a summer festival as the opening event have been floated, and the stadium management has asked the Heroes for their help. [HELIOS] has agreed to fully cooperate for the sake of the city. Not only will the Heroes perform at the festival, but they'll also be helping with the event itself, working across sector boundaries to prepare for the festival's opening. However, one problem after another arises... Furthermore, behind the scenes, [Eclipse] and his allies are secretly plotting. Will the "Summer Festival" be able to open safely?

A Bakuken stage production centered on the Shinsengumi, continuing the alternate-history sword-fighting anthology created by Yoko Taro and Ichidai Matsuda.