Kaoru Matsubara

She transforms using the phrase "Powered Buttercup" and uses a Daruma Otoshi hammer. Like the original Buttercup, Kaoru is a tomboy and is the most easily enraged of the three. She is known at school for being the most athletic girl as she plays tennis, practices martial arts, and numerous other activities, and spends a great deal of time watching sports on television. She is especially good at soccer due to her strengthened determination after receiving new soccer cleats when she was younger. This may be part of the reason why she has so many fangirls, much to her dismay.

She dislikes girls, who she considers very "girly". This includes Momoko and Miyako. This, in addition to the fact that she hates skirts, makes Kaoru the most reluctant of the girls, only joining due to the power it has given her. In later episodes, she begins to care about Momoko and Miyako and is no longer reluctant about joining them in whatever they do, but she often tries to act calm and indifferent.

She speaks with a hard and masculine edge and rarely uses honorifics when speaking. Her greatest fear is ghosts. Kaoru lives with her father, who is a professional masked-wrestler, mother and two brothers, one older and one younger. She is represented by stars.