"How to Keep a Mummy" centers around Sora Kashiwagi, a high school student who receives an unexpected gift from his father, an adventurer and archaeologist. The gift is a small, adorable mummy named Mii-kun, which is only about 15 centimeters tall. Despite its tiny size, Mii-kun is a living, breathing creature with a gentle and affectionate personality. Sora quickly grows attached to Mii-kun and takes on the responsibility of caring for it, learning about its needs and quirks as they bond.

As the story progresses, Sora’s life becomes intertwined with other classmates who also possess supernatural companions. These include Tazuki, who has a dragon-like creature named Conny; Daichi, who cares for a shy yeti named Suu; and Aya, who is accompanied by a mischievous shiba inu spirit named Nico. Each of these creatures has its own unique personality and abilities, adding variety and charm to the narrative. The group forms a close-knit circle, sharing their experiences and supporting one another as they navigate the challenges of raising their unusual pets.

The series explores themes of friendship, responsibility, and the joy of forming connections with others, both human and non-human. The interactions between the characters and their supernatural companions are heartwarming and often humorous, highlighting the bonds that develop through care and understanding. While the story is lighthearted and episodic in nature, it occasionally delves into more emotional moments, particularly when addressing the origins and needs of the creatures.

The main characters are well-defined, with Sora serving as a relatable protagonist who grows more confident and compassionate through his relationship with Mii-kun. Tazuki, Daichi, and Aya each bring their own perspectives and dynamics to the group, creating a balanced and engaging ensemble. The supernatural creatures, particularly Mii-kun, are endearing and play a central role in driving the narrative forward.

Overall, "How to Keep a Mummy" is a wholesome and charming series that combines slice-of-life storytelling with supernatural elements. It emphasizes the importance of empathy, care, and the joy of forming meaningful connections, making it an enjoyable and accessible watch for audiences of all ages.