Minami Toba, a history teacher at Motosu High School, begins her tenure as a substitute covering a maternity leave. By day, she maintains a composed, professional facade, her eyes perpetually half-lidded behind glasses during lectures. By night, she sheds this restraint, earning the monikers "Miss Chug" and "Gubi-nee" from her ritual of buying six 500ml beer cans daily from a local liquor store. Her dual nature surfaces in her gaze—soft and unfocused while teaching, sharp and alert when intoxicated.

Her entanglement with the Outdoor Activities Club starts during a lakeside camping trip, where a tipsy encounter with Rin Shima and Nadeshiko Kagamihara leaves Rin convinced she’s glimpsed a ghost. Later, Minami stumbles into the role of club advisor after questioning students’ unauthorized bonfire on school grounds. Reluctant at first, she draws on childhood memories of family camping trips with her younger sister, Ryōko Toba, gradually embracing her duties.

As advisor, Minami balances irreverence with responsibility. She rescues Chiaki Ōgaki’s group during a poorly planned winter excursion and oversees major trips like the Izu camping journey, where a bet with Chiaki prompts temporary sobriety—until a hot spring mishup reignites her cravings, forcing her to enlist a driver. This period also unveils her newfound solace in butter cookies.

Her evolution from viewing the club as a chore to actively joining shrine visits and winter camps mirrors her growing connection to the students. She frequents Chiaki’s workplace, bonding over shared interests, her approachability offsetting her raucous reputation. Though her comedic struggles with alcohol persist, post-Izu moderation hints at maturity, balancing her spirited persona with professionalism.

A Suzuki Hustler—a yellow-and-white mini SUV—anchors her practicality, while her surname nods to her family’s coastal roots in Toba, Mie Prefecture. Childhood adventures under stars with Ryōko now fuel her guidance of the club, weaving personal history into mentorship.