Yumi is a human captive held within the dystopian settlement called the Secret Garden. This society is ruled by children who possess psychic abilities. Under their rule, adults are forced to participate in sexual orgies for reproduction. Yumi is condemned to sexual servitude within this regime.

Her captivity includes repeated sexual assaults by a tentacle monster controlled by the child rulers. These prolonged and graphic assaults occur within a pit while the children observe. During the attacks, tentacles penetrate her both orally and vaginally, constituting explicit sexual violence.

Yumi's suffering inflicts psychological torment upon another captive, Ken, who is forced to witness her violations. The child rulers utilize her agony to manipulate Ken into compliance, coercing him into sexual acts with adult women during the orgies. Her ongoing rape and degradation function as tools to break Ken's resistance.

No prior background or subsequent resolution for Yumi is documented. Her role centers entirely on her victimization during the Secret Garden sequence.