Kaoru (かおる) is a young girl residing in contemporary Japan with her parents and younger brother, Tatsuya. Featured in "Super Mario no Shōbōtai," she is first seen playing *Super Mario Bros. 3* with Tatsuya, growing annoyed by his unsolicited gameplay tips. When her mother assigns her grocery shopping, Kaoru discovers firework sparklers in a kitchen drawer and secretly pockets them. She later persuades Tatsuya to accompany her to a car junkyard to light the sparklers unsupervised. During this reckless activity, discarded embers set a nearby garbage can ablaze, causing panic. Mario and Luigi intervene to extinguish the fire, lecturing the siblings sternly about fire hazards and the dangers of irresponsible behavior, leaving Kaoru visibly shaken.

That evening, Kaoru remains too unsettled for her usual pastimes. A minor earthquake triggers her memory of the fire safety advice, prompting her to urgently instruct her mother to shut off the gas stove, preventing a potential disaster. She further demonstrates heightened vigilance by quickly stomping out a cigarette dropped by her father before it can ignite the carpet. Moments later, she alerts emergency services upon spotting a fire in a neighboring apartment building.

Kaoru's relationship with Tatsuya involves typical sibling dynamics, sharing activities and mutual concern despite occasional friction. She exhibits protectiveness towards her brother, silently urging secrecy about their fireworks misadventure. Her character development centers on a transition from initial carelessness to proactive fire safety awareness, directly applying the lessons learned from Mario and Luigi's intervention.