Shōma Ameku is a high school student whose romantic confession ignites a relationship with Kiriko Kiyuna. He remains unaware of her past as a Daimidaler mecha pilot until her direct revelation.

Deeply loyal to Kiriko, Shōma consistently braves threats to protect her, though he often requires rescue himself. Their relationship features frequent public displays of affection, ranging from romantic to overtly erotic, drawing school complaints. These interactions also stimulate Kiriko's Hi-ERo particles, essential for powering the Daimidaler robot.

During the Penguin Empire conflict, Shōma undergoes a drastic change when transformed into a penguin in Episode 10. This compels him to leave Kiriko and join the Empire, causing her significant distress and fueling her resolve to reclaim him. The situation resolves in Episode 12 when Henry intervenes, reverting Shōma to human form and enabling his return.

He attends the same school as Kōichi Madanbashi, serving as his senior alongside Kiriko. Shōma's ordinary school life starkly contrasts with his entanglement in the larger conflict through his bond with Kiriko.