Kuroi Souya is a high school student leading a quiet life, even though he has no recollection of his past. However, one day his town comes under attack by one of the enigmatic Nebula Weapons. Alongside the cat-like "Sensei" and the gothic lolita Ginko, Souya is pulled into a conflict against... seven superheroes tasked with protecting the town! What drives Souya to fight? The answer is hidden within his memories.