Elena Himekawa is a 14-year-old idol affiliated with P.O.G. (Puzzle of God), holding the title "Antoinette." She hosts the popular show "Puzzle Kingdom," initially displaying an arrogant, cold personality towards opponents, embodying a "cold princess" persona. Her appearance features bright pink waist-length hair swept to the left and pink eyes; she often wears a black skirt, white shirt, necktie, and jacket, later changing to a pink shirt, purple skirt, light blue jacket, black stockings, and brown shoes.

Initially selfish, Elena refused displeasing tasks and expressed disdain for people with friends, including Kaito Daimon's group. After losing a puzzle battle against Kaito, her personality shifts significantly. She becomes approachable, cheerful, and develops genuine concern for others, notably worrying about Gammon Sakanoue joining P.O.G. and urging Kaito and Nonoha Itou to help revert him.

Elena harbors romantic feelings for Gammon, accidentally confessing them in front of Kaito and Nonoha. Her P.O.G. role involves challenging solvers on "Puzzle Kingdom," such as orchestrating a life-threatening car-based sliding puzzle where participants must escape before a falling truck crushes them. Following her development, she transitions from antagonist to occasionally assisting Kaito's allies, particularly in efforts to protect or redeem Gammon.