Naoki Matsudo, childhood friend of protagonist Kei Anno, joins him as a pilot in the international organization SPIRITS to operate the mecha Devadasy against alien forces. When primary co-pilot Amara withdraws, Naoki volunteers, driven by simmering jealousy and unspoken romantic feelings toward Kei. Her role mandates wearing a specialized one-piece swimsuit to synchronize with the mecha’s systems—a requirement that underscores the physical and psychological demands of her duty.

Tensions escalate when Kei, compromised by nanomachine manipulation and external coercion, violently confronts her in a moment of fractured judgment, exposing the corrosive strain of their environment. Later, during the climactic battle, Naoki is seized by an alien force and coerced into piloting a corrupted version of Devadasy. Though rescued by Kei, their relationship—and her ambiguous, possibly familial tie to Amara—remains unresolved, lingering as a quiet undercurrent beneath the mission’s aftermath.

Her arc weaves rivalry, loyalty, and raw vulnerability into the narrative’s broader examination of human bonds under extreme pressure. While her origins beyond SPIRITS recruitment remain unexplored, her choices and conflicts with Kei and Amara anchor her as a figure balancing personal fragility with the stark demands of duty.