"Monster Musume" is a manga series that blends comedy, romance, and fantasy elements, centering on the interactions between humans and liminal beings—humanoid creatures with animal traits. The story begins when Kimihito Kurusu, a young man living a relatively ordinary life, becomes a host for a cultural exchange program between humans and liminals. His life takes a dramatic turn when a lamia named Miia arrives at his home as the first participant in the program. The government assigns Kimihito to care for Miia, and his household quickly expands as more liminal girls join, each with unique traits and personalities.

Miia, a snake-like lamia, is affectionate and possessive, often displaying jealousy when other girls vie for Kimihito's attention. Papi, a harpy, is carefree and childlike, contrasting with Miia's intensity. Centorea, a centaur, is proud and chivalrous, adhering to a strict code of honor. Suu, a slime girl, is curious and adaptable, capable of changing her form. Mero, a mermaid, is elegant and romantic, often caught in dramatic fantasies. Rachnera, an arachne, is mature and composed, though her spider-like traits initially unsettle Kimihito. Each character brings distinct dynamics to the household, creating comedic and heartfelt situations as they navigate their relationships with Kimihito and each other.

The narrative explores the challenges of coexistence between humans and liminals, often highlighting cultural misunderstandings and societal prejudices. Kimihito, despite his initial reluctance, grows into a responsible caretaker, striving to balance the needs and emotions of his diverse housemates. The series frequently incorporates slapstick humor, romantic tension, and lighthearted moments, while occasionally addressing deeper themes such as acceptance and the complexities of interspecies relationships.

As the story progresses, additional characters are introduced, including government agents like MON, the organization overseeing the exchange program, and other liminals who further complicate Kimihito's life. The series maintains a focus on the daily lives of its characters, blending episodic adventures with overarching developments in their relationships and the broader world of humans and liminals. Through its mix of humor, romance, and fantasy, "Monster Musume" presents a unique exploration of coexistence and connection in a world where the boundaries between species are increasingly blurred.