Masumi Nishino, a first-year in Seitetsu Gakuin High School’s class 1-3, balances her dual roles as a spirited school journalist and charismatic event emcee with an impulsive streak. Her extroverted nature fuels a journalism style marked by sensationalism, often embellishing facts to craft gripping articles, while her disregard for boundaries contrasts sharply with her discreet handling of confidential duties as the female liaison for the Normal Relations Between Boys and Girls Underground Committee. Childhood ties bind her to Akane Mishima, a reserved rebel Kämpfer, their friendship anchored in mutual goth-fashion interests despite opposing temperaments.

Masumi’s article falsely labeling Natsuru Senō’s female persona as a lesbian sparks rampant student curiosity, intertwining her reporting with the Three Beauties’ documentation of his dual life. Though her actions amplify Natsuru’s visibility, her focus remains fixed on unraveling mysteries rather than romantic entanglements. Academically middling, she drifts through classes but finds solace in music-listening naps. Unaffiliated with campus factions, she navigates social dynamics with calculated exuberance, her B-type blood and surname Nishino (西乃—"west from") hinting at a personality both vibrant and unpredictably grounded.