Momen Sanada hails from poverty, driving her to seek work in a nearby city. Her natural clumsiness kept getting her fired or scolded, instilling a deep fear of making mistakes, a fear that persisted even after she joined the secret military unit aboard the flying battleship Amanohara.

Assigned to the Lime Unit, she pilots the red, sword-wielding unmanned mecha Yukimura, powered by her supernatural Konjiki ability to manipulate fire. She defends the Amanohara against Russian spiritual forces during the Russo-Japanese War.

Physically strong yet notably immature and clumsy, Momen exhibits high energy but constantly trips and falls, often accidentally exposing her underwear. Despite daily ineptitude, she possesses fierce loyalty and dedication to her teacher, Shintaro Umakai, whom she calls "brother" due to his resemblance to her real sibling. This motivates her to wake him every morning and declare she'll do anything for him.

Her character features in the two-part OVA *The South Island Dream Romantic Adventure*, where the Amanohara docks on an island for repairs during a festival. While pursuing enemies, she engages in comedic efforts alongside unit members to win Shintaro's romantic attention. The OVA highlights her tendency toward accidental risqué situations: partial nudity while cleaning in only an apron, and going without underwear while her sole pair is washed.

Her feelings for Shintaro evolve from familial affection into romantic attraction, a shift mirrored by other unit members. Comic interactions include mistaking Sarasa Honda's breasts for meat buns and trying to bite them. Participation in group dances and festivals shows her growing integration despite initial social awkwardness.

Her background remains rooted in economic hardship, with only a brother mentioned. The OVA concludes with Momen and the unit sacrificing their Konjiki powers to revive Shintaro after a near-fatal spiritual attack, resulting in her losing her supernatural abilities.