Fumika Momoshina serves as an Actress for Narikozaka Manufacturing, conducting combat operations in specialized powered armor. Her surname meaning "Encyclopedia" reflects vast knowledge, while her given name's characters for "writing" and "praise" hint at intellect and esteem. She studies alongside Kaede as a second-year student at Seijo University First High School, though they share no direct connection.

Outwardly calm and serious, Fumika speaks candidly with low tolerance for irresponsibility. Despite pessimism, she demonstrates diligence and reliability, proactively supporting struggling colleagues through practical aid and mentorship.

Her combat loadout features the Brigantia Mk3 T Top Gear and Brigantia Mk3 B Bottom Gear armor systems, armed with the Hegel M3 Bazooka, missile racks, and Champolion Mk3 Sword. Tactical accessories include the Candelaria.

Interactions showcase her multifaceted nature: competing against maintenance crews in survival games, assisting at an Actress-themed café, confronting wildlife threats during a hike, and engaging in meta-narrative humor when a detective-themed episode abruptly cut her dialogue. She joined community motorcycle gang reforms and Narikozaka promotional videos, though maintenance staff were edited out for perceived lack of appeal.

Fumika maintains longstanding but contentious friendships with fellow Actresses Shitara Kaneshiya and Yumi Yotsuya. As a senior figure, she guides newer recruits like Yotsuyu Hirasaka despite occasional friction. Her reading hobby is evidenced by book and glasses accessories integrated into her gear.

Post-credits scenes occasionally feature her in bars with other characters, contributing to slice-of-life vignettes beyond main narratives.