The famous Een hero Honest Oki had eight sisters: Oka, Obo, Ona, Ola, Ozi, Ori, Opi, and Oji. Oki often complained about living with so many girls, though he did come to miss them once he moved away from home to apprentice as an inventor with Ratchet Ringtail.

During the tyrannical rule of Burdock Brown, the Openheart sisters were sent to work in the Dragon Jaw salt mines, along with their parents. Only Oji and Opi managed to escape this fate, hiding out in the family's mushroom house. Unfortunately, they were eventually captured by Captain Rinkle and taken before Burdock to be judged for crimes of being critters.