In Touhou 16: Hidden Star in Four Seasons, Despite being midsummer in Gensokyo, the seasons are in disarray: cherry blossoms are blooming at the Hakurei Shrine, Youkai Mountain is experiencing autumn, and the Forest of Magic is blanketed in snow. Additionally, fairies have become unusually powerful. The protagonists- Reimu, Marisa, Aya, and Cirno- investigate and discovers the Land of the Backdoor, a mysterious dimension where our protagonist meet a secret god, the person responsible for it.
Reimu Hakurei – The miko of the Hakurei Shrine who maintains the Great Barrier and resolves incidents.
Marisa Kirisame – A self-taught magician who collects magical items and frequently joins Reimu in investigations.
Aya Shameimaru – Aya is a tengu bird, she is a reporter with her own newspaper and she resides in youkai mountain.
Cirno – An ice fairy who resides in the misty lake she has also been empowered by the effects of the seasons.
Eternity larva – A butterfly fairy who embodies the insect life cycle, from larva to adult. Normally gentle, she becomes unusually powerful during the season of spring, possibly due to an external force.
Nemuno Sakata – A solitary yamanba (mountain witch) who prefers a primitive lifestyle. She can create sanctuaries and is known for her asocial nature, avoiding interaction with others. Despite her reclusive tendencies, she occasionally engages with outsiders in a businesslike manner.
Aunn Komano – A komainu (guardian lion-dog) who guards sacred places like the Hakurei Shrine. She possesses the ability to detect Shinto and Buddhist influences and often takes it upon herself to protect these sites. Though not particularly strong, she is determined and enjoys the role of a guardian.
Narumi Yatadera – A magical jizo statue brought to life by the magical energies of the Forest of Magic. She has the ability to control life force and was initially unaware that she was the source of the seasonal anomaly.
Mai Terada – FIfth stage boss, Mai is one of the two dancers that serve Okina. Mai has the power to plant doors on others' backs.
Satano Nishida – Also the fifth stage boss, the second of the two dancers that serve Okina. Satono can manipulate vitality, They serve as intermediaries for Okina, testing others to find a worthy successor.
Okina Matara – Fifth stage and Extra stage boss, Okina is a secret goddess capable of controling seasons among other abilities. She orchestrates the seasonal anomaly by empowering others through the planting of doors on their backs, aiming to showcase her power and find a new servant. Her true intentions remain shrouded in mystery.