Kuromaru Manpuku appears as a supporting character across multiple official media entries including the anime, an OVA, and video games. She possesses thigh-length pink hair tied in low pigtails with yellow bows, left-side bangs, and light-green eyes, complemented by a notably tall and curvaceous physique. Her standard attire features a blue maid uniform with white frills, a headpiece, and apron, accessorized with blue ribbons on her upper arms. Shinobi-inspired elements include gauntlets, thigh-high boots with metal detailing, a red waist rope fastened by a shuriken buckle, and an oversized rolling pin strapped to her back. During jet races, she dons either a full-body black-grey wetsuit with a black maid headpiece or a red bikini with a white headpiece.

Personality-wise, she exhibits an excitable and agreeable demeanor, particularly enthusiastic about competitions, and speaks with the verbal tic "Na No Da." Her near-bottomless appetite manifests through frequently producing and consuming oversized onigiri, aligning with her surname’s meaning ("full stomach"). Profound loyalty to Kaguya Shijyuin—rooted in her family’s generational service as kunoichi to the Shijyuin household—drives fierce protectiveness and a willingness to prioritize Kaguya’s needs over her own well-being, sometimes working to exhaustion. She reacts defensively when her shinobi heritage faces stereotyping.

Her background establishes her as a student at Musashino Girls' High School and Kaguya’s personal kunoichi attendant, blending maid duties, bodyguard responsibilities, and racing partnerships. This generational bond underpins her unwavering dedication.

In the anime’s narrative, she debuts alongside Kaguya in the first episode, challenging Rin Namiki and Misa Aoi to a Kandagawa river jet race. As Team Dress’s Shooter, she demonstrates combat proficiency by targeting opponents’ vehicles and clothing with high-pressure water fire, securing their initial victory. The video game expands her arc: Team Dress enters the Kandagawa Cup to prevent Kaguya’s father from shutting down their racing program. Kuromaru trains excessively, neglecting her health until Kaguya deliberately delays a crucial race to force her rest—revealing reciprocal care. Rival teams unexpectedly postpone the race, enabling Team Dress to compete and win the Cup, securing their future.

Game arcs further explore her involvement. In the Kandagawa Jet Girls storyline, Team Dress loses a "river ownership" bet race against Rin and Misa and later withdraws from the Cup, implicitly due to Kuromaru’s exhaustion. The Unkai Surfers arc depicts her discomfort when the team fixates on shinobi stereotypes. During the Grindcore narrative, Team Dress acts as rivals to correct Grindcore’s win-at-all-costs mentality; their victory imparts a lesson about jet racing’s true spirit. The OVA shows her participating in a jet racing promotional video project, appearing in Kaguya’s rejected training montage and later observing other teams’ attempts with increased dialogue.

Her relationship with Kaguya remains central across media. They function as inseparable jet racing partners (Kaguya as Jetter, Kuromaru as Shooter) and daily companions, with Kuromaru performing maid duties. Their bond transcends service, reflecting mutual best-friend status. Kaguya demonstrates deep concern by sacrificing race opportunities for Kuromaru’s rest and frequently treating her to meals. Kuromaru interacts minimally with others, though she recognizes Misa as Rin’s teammate and voices opinions on shinobi perceptions.