Mana is a second-year Coppelion—one of the genetically engineered girls who constantly emit neutrons, making them walking biohazards to anyone but each other. She's among the most powerful of her kind, with psychokinetic and gravity-manipulating abilities that let her fly (which she does almost constantly), levitate objects, deflect bullets, and unleash violent shockblasts.
Her main motivation is working under Dr. Coppelius, who's promised to fix what makes her and the others "defective." She defected from the Exploration Unit alongside her best friend Meisa, following the same path as the Ozu sisters.
What really defines Mana is how quiet and stoic she is—so much so that enemies find her genuinely unsettling. When she first showed up in volume 10, she didn't speak for an entire volume. Even after that, she remains mostly silent, letting her abilities do the talking.
Content compiled by AnimeList.moe from publicly available sources.