Hinako Tondabayashi is the twenty year old daughter of Kenzaburo Tondabayashi, a fifty-two year old civil servant who is the protagonist of the story. She is a central figure in the real world and serves as a crucial link to the fantasy setting her father becomes trapped in. A proud and self-described purebred otaku, Hinako was raised by parents who were themselves passionate about anime, manga, and games, and she carries on this legacy with great enthusiasm. She is especially fond of otome games, romantic simulation titles typically aimed at a female audience, with her absolute favorite being Magical Academy Love & Beast, a game she knows inside and out. Often seen with her glasses, she is a gamer chick who plays openly in her living room, unconcerned with hiding her hobbies from her family. Rather, she shares a close and unique bond with her father, built on friendly camaraderie over their joint interests; they frequently bond by posing or quoting famous lines from classic anime and tokusatsu shows together.

Hinako’s personality is defined by her geek pride and her strong sense of empathy, even toward fictional characters. She has a deeply affectionate and respectful relationship with her parents, viewing them as pioneers of otaku culture, though she can occasionally find her father’s advice a bit bothersome in the way young adults sometimes do. This respect is paired with a notable level of responsibility, as she is capable of handling household chores and preparing dinner when needed. Her personal philosophy as a gamer is telling: when playing Magical Academy Love & Beast, a game with random elements for summoning creatures, she belongs to the no-reset faction. She refuses to undo a summon because she finds it too cruel to erase a being that has come into existence, even if it is just data in a video game.

Her primary motivation throughout the story is the welfare of her father. After he is struck by a car and his consciousness is absorbed into the world of her favorite video game, Hinako is the first to realize what has happened. Unlike a typical player, she becomes an active participant in the game's world from the outside, determined to protect and support Kenzaburo, now inhabiting the body of the villainess Grace Auvergne. Hinako’s role in the story evolves from a simple observer playing the game on her couch to a vital, otherworldly support agent. When Grace performs a beast summoning, Hinako is presented with a choice for the first time, and she intervenes physically by literally putting her hand into the television screen to mix her own magic into the summoning process. After this event, she continues to assist her father by using Orion, Grace’s summoned beast, as a conduit to communicate with him and offer guidance.

Her deep knowledge of the game’s mechanics and story routes is her most significant ability. While Kenzaburo is lost inside the world, Hinako functions as his guide, using her expertise to help him navigate the plot and use the game's systems to his advantage. She later discovers that Grace’s situation is connected to the real world through a character named Adrian’s laboratory, a revelation that allows her to send letters into the game to update her father on his real-world condition. Throughout the crisis, she works closely with her mother, Mitsuko Tondabayashi, to monitor Kenzaburo in the hospital and coordinate their efforts to support him from both sides of the dimensional divide. Her character development is subtle, revolving around the shift from being a passive consumer of an otome game to an active, empowered protector of her family, using her niche passion for gaming as a tool for genuine heroism.