Aoi Muto is a third-year student at Monong University, a faculty of agriculture, and a member of Professor Keizo Itsukis laboratory. Known on campus as Miss Agriculture, she possesses a striking appearance that earns her this title, though she is equally recognized for the dark circles that often appear under her eyes. As the only practicing undergraduate in the professor's lab, she serves as a junior colleague to the graduate student and lab assistant, Haruka Hasegawa.

Mutos personality is defined by a remarkable toughness and a free-spirited, almost feral independence. She travels the world alone to collect fermented foods for research, an endeavor that has led to significant hardships. On one such trip, she was stranded on the opposite side of the globe when she was unable to board a plane with her collected samples. Undeterred, she managed to return to Japan by hitchhiking and taking trains, wearing the same unwashed clothes for two weeks. Her first appearance in the series is memorable for her disheveled state after one of her fermented samples exploded, covering her in a black, odorous liquid.

Her motivations are closely tied to her academic and personal life. She is dedicated to her studies in fermentation and aims to attend graduate school, following in Hasegawas footsteps. Unlike Hasegawa, however, Muto prefers to work directly in the field rather than in a laboratory setting. Her personal life is marked by a past romantic betrayal. She once worked grueling part-time jobs to save money to live with her boyfriend, who subsequently left her a note saying he had found someone else and fled with her savings. To cope with this trauma, she has developed an intense belief that he must have been abducted by a UFO, a fantasy that helps her escape from the painful reality of the situation. This belief fuels her role as the chairman of the universitys UFO Research Society.

In the story, Muto often acts as an eccentric and unpredictable senior figure among the younger students. She has a deep fondness for alcohol, particularly beer, and is frequently seen drinking during the day, to the point of being described as a near-drunken character. Her behavior becomes notably uninhibited when she drinks; she has shown a strong attraction to women, which has led to several incidents, including a notable encounter with fellow student Hazuki Oikawa. Her drinking has also caused larger problems, such as when she caused a disturbance during the Miss Agriculture contest while intoxicated.

Key relationships include her professional bond with Haruka Hasegawa, whom she assists and looks up to as a role model. She has a close and complicated relationship with Hazuki Oikawa, with whom she had a sexual encounter that was implied to be influenced by an aphrodisiac and alcohol. Muto interacts with the other members of Professor Itsukis lab, including the protagonist Tadayasu Sawaki, who, with his unique ability to see microbes, once observed the microorganisms on the floor to deduce the nature of her encounter with Oikawa.

Throughout the series, Muto shows development by becoming more focused on her academic path, deciding to aim for graduate school. She also takes a leading role in significant events, such as the schools Oktoberfest festival, demonstrating her growing investment in her field of study and her community at the university. Her notable abilities include an extensive, hands-on knowledge of fermented foods gathered from her global travels and an incredible resilience for surviving difficult journeys and situations that would deter most people.