Miki Hosokawa is a student in the class of Meisuke Nueno, known as Nube. She is one of the most outspoken and mischievous members of the group, initially characterized by her love of gossip and her tendency to talk incessantly about rumors, especially those involving her teacher. This talkative nature once led her into a dangerous encounter with a tattletale youkai, an experience that marked a turning point in her development. After that incident, she began to channel her curiosity into serious study of the supernatural, building a deep and practical knowledge of spirits, youkai, and various occult matters. Her expertise grew to the point where even Nube sometimes consulted her for information he did not possess. Despite this scholarly turn, her motivations remain mixed: she often seeks supernatural solutions for personal gain, whether to feed her rumor mill or to find a quick way to get rich.

Miki is extremely vain about her physical appearance, particularly her figure, and takes pride in her changing measurements throughout the series. She flaunts her appearance whenever she can. Her personality is lively and mischievous, which often stirs up trouble and laughter among her classmates. She is curious and playful, but also possesses a practical side that drives her to research the occult.

In the story of Jigoku Sensei Nube: Kyōfu no Natsu Yasumi! Ayashi no Umi no Densetsu, Miki joins her class on a summer trip to a small island for beach activities. When the group hears a foreboding legend about a creature called the sea spider from an old island resident, Miki is among those who become involved in the mystery. Her accumulated spiritual knowledge and her ability to become a rokurokubi—a supernatural ability that allows her to stretch her head and neck to travel unseen—prove useful in uncovering the truth behind the legend and the appearance of a mysterious girl on the beach.

Her key relationships include her fellow classmates, such as Hiroshi Tachino, Kyoko Inaba, and Katsuya Kimura, with whom she shares both everyday school life and supernatural adventures. She respects Nube as a teacher and occasionally seeks his guidance, though she also teases him. Over the course of her appearances, Miki evolves from a mere gossip into a capable and knowledgeable individual who uses her unique talents to help navigate the spiritual threats her class encounters. Her development reflects a balance between her personal vanity and her genuine growth as a student of the supernatural.