Kayoko Uchida cohabitates with the protagonist as his girlfriend and primary financial provider through her insurance firm job. Her income sustains their household, while her partner contributes minimally and habitually requests funds for pachinko gambling. This dependence fuels recurring tension, prompting Kayoko to voice frustration over his unemployment and domestic absence. Despite arguments, mutual affection sustains their relationship, though she intermittently threatens to leave without acting on it.

She handles most household duties despite resenting chores, particularly cooking. This aversion sparks an unconventional friendship with General Vamp, leader of the antagonistic Florsheim organization. They maintain cordial conversations where Kayoko solicits housekeeping and recipe advice, occasionally inviting him home. She openly contrasts Vamp's cooperative nature with her partner's perceived inadequacies, intensifying domestic friction. Their dynamic sometimes features collaborative cooking demonstrations.

Outside work and chores, Kayoko engages with other Florsheim members, maintaining civil ties with assorted monsters who assist during practical tasks like relocating households. Her visual design evolved during manga serialization, shifting from an initially plain, heavier appearance to a more conventionally attractive look, which the anime adaptation adopted from its outset.