Mika Masuko is the chief reporter and editor for Cinq Lumières Middle School's newspaper, Cinq Lumières News. She sports short brown hair, glasses, and the standard school uniform, usually equipped with a camera and voice recorder. Her defining trait is an intense passion for journalism, especially chasing major scoops involving school mysteries or the Pretty Cure team. This fervor often led to overly aggressive reporting tactics, straining peer relationships and ultimately causing the rest of the newspaper club to resign. Left alone to handle all editorial duties, Mika turned to relying on rumors and quicker, less-researched stories to manage the workload, fueling periods of self-doubt and isolation. Despite outward confidence, she privately envied the close friendships of others like Karen Minazuki and the core group of girls, revealing her underlying loneliness.

Her persistent investigation into the Pretty Cure's identities centered on students Nozomi Yumehara, Rin Natsuki, Urara Kasugano, Komachi Akimoto, and Karen Minazuki, noting their frequent gatherings coinciding with Cure appearances. While she often neared confirming their identities, distractions usually intervened, notably her crush on Nuts in his human form, which diverted her focus. She once captured photographic proof of the Cures but, advised on ethical reporting, chose not to publish it without their permission. Her reporting shifted towards everyday student life, covering Urara Kasugano's lunch habits, Rin Natsuki joining the futsal team, or features on Karen Minazuki's routines.

A critical reporting error damaging a futsal team captain's reputation triggered a crisis of confidence. Feeling responsible and isolated, Mika decided to resign and discard her reporting materials. While sorting old belongings, she rediscovered earlier collaborative work with former club members, including a positive article about a lost dog, rekindling her initial journalistic passion. This reflection coincided with an attack by the villain Bunbee; the Pretty Cure intervened to protect her. Afterwards, the Cures voluntarily granted her an exclusive interview. During their talk, they asked if she believed she could find meaningful friendships like theirs, prompting her to reconsider resignation. She resumed her role, corrected the futsal article, and published a piece on the Pretty Cure respecting their anonymity. Though acknowledging no resemblance between the Cures and her suspected students, she committed to reporting their heroic deeds while prioritizing everyday school news and ethical journalism.

Her name functions as a pun on the Japanese term "masukomi," an abbreviation for "mass communication," reflecting her professional focus; she occasionally requested others to address her using this term. Characters with similar surnames and journalistic roles appear in other Pretty Cure series, such as Masuko Miyo in *Happiness Charge Pretty Cure!* and Masuko Michio in *Healin' Good♥Pretty Cure*, with no established familial or direct connection to Mika.