"How to Keep a Mummy" centers around Sora Kashiwagi, a high school student who receives an unexpected package from his father, an adventurer often traveling abroad. Inside the package is a small, adorable mummy named Mii-kun, who becomes Sora’s responsibility. Despite initial confusion, Sora quickly grows fond of the tiny mummy, who is surprisingly affectionate and eager to help. Mii-kun’s presence introduces Sora to a world of supernatural creatures, as he befriends others who also care for unique beings.

The narrative expands as Sora meets classmates and friends who share similar experiences. Tazuki, a quiet and reserved boy, cares for a dragon-like creature named Conny, while Kaede, a cheerful and energetic girl, looks after a small yeti named Suu. Together, they navigate the challenges of raising their unusual companions, blending slice-of-life moments with lighthearted humor and occasional emotional depth. The interactions between the human characters and their supernatural charges highlight themes of responsibility, friendship, and understanding differences.

The story progresses through episodic adventures, often focusing on the daily lives of Sora and his friends as they learn to coexist with their otherworldly companions. Mii-kun’s curiosity and innocence frequently lead to comedic situations, while the bonds between the characters deepen over time. The manga balances whimsical, fantastical elements with relatable human experiences, creating a heartwarming and engaging narrative. The relationships between the humans and their supernatural companions serve as the core of the story, emphasizing mutual care and growth.