Miyubi Shishio is a female sloth attending Seton Academy, marked by long blonde hair, purple eyes, and moss kept on her head as emergency sustenance. Her tall stature grows further after a significant timeskip. Biologically constrained by sloth traits, she moves extremely slowly and faces fatal overheating from minimal exertion like walking or bathing. She uniquely revives shortly after dying from such stress. In water, she swims with unexpected speed, showcased during a school field day race.

Lonely due to her species' solitary nature, Miyubi finds companionship when Ranka Ookami invites her to the Cooking Club. There, she forges bonds, particularly with Jin Mazama and Ranka. Jin assists her daily, carrying her during exhaustion-induced collapses and rescuing her from drowning in a bath incident, actions she gratefully acknowledges, signaling her emotional shift from isolation to belonging.

Academically, Miyubi reveals hidden scientific genius, actively contributing to midterm study sessions. Her past includes a brief stint as "Slow Cyclone," a card-game champion among donkeys, retired due to physical strain from handling heavy cards.

In her future, Miyubi becomes a scientist who invents a time-leaping device, pivotal for Jin's efforts to prevent Ranka's death across timelines. Post-timeskip, she uses an automatic motorized wheelchair for mobility, her vocabulary and scientific contributions growing notably advanced.

Thematically, she parallels Manako Kagami in high mortality risks from species traits. Her enduring "Odd Friendship" with Ranka bridges their contrasting energy levels and temperaments.