Gramma serves as maternal grandmother and guardian to Yuna Kamihara, sharing their home on the fictional Izayoi Island within the Ryukyu archipelago. She assumes primary caregiving duties following the death of Yuna's mother during a typhoon, compensating for the frequent absences of Yuna's father, a marine biologist. Her late husband, Yuna's grandfather, formerly operated a karate dojo on the island and gifted Yuna a moonsand charm for her karate studies before his departure.

She holds a steadfast belief in the yōkai inhabiting Chitama Forest, a conviction setting her apart from most islanders. This faith leads her to introduce both Stitch and Yuna to the Chitama Spiritual Stone, a mystical artifact sustaining the yōkai's lifeforce and capable of granting wishes to those who complete 43 good deeds. After Stitch arrives, she incorporates him into their household alongside Dr. Jumba Jookiba and Agent Pleakley, extending familial acceptance to these extraterrestrial visitors.

Her involvement centers on maintaining the household and supporting Yuna and Stitch’s activities. She provides stability during Stitch’s quest to accumulate good deeds for his wish to gain ultimate power, though her direct participation in these quests lessens as the focus shifts to Yuna and Stitch’s adventures. When Yuna and Stitch relocate to Okinawa New Town in the third season, she remains on Izayoi Island. Gramma does not appear in the post-series television specials *Stitch and the Planet of Sand* (2012) or *Stitch! Perfect Memory* (2015), nor in other franchise media such as *Stitch & Ai*.