For weeks, Atsushi Nakajima's orphanage has been plagued by a mystical tiger that only he seems to be unaware of. Suspected to be behind the strange incidents, the 18-year-old is abruptly kicked out of the orphanage and left hungry, homeless, and wandering through the city. While starving on a riverbank, Atsushi saves a rather eccentric man named Osamu Dazai from drowning. Whimsical suicide enthusiast and supernatural detective, Dazai has been investigating the same tiger that has been terrorizing the boy. Together with Dazai's partner Doppo Kunikida, they solve the mystery, but its resolution leaves Atsushi in a tight spot. As various odd events take place, Atsushi is coerced into joining their firm of supernatural investigators, taking on unusual cases the police cannot handle, alongside his numerous enigmatic co-workers.

High school freshman Houtarou Oreki has but one goal: to lead a gray life while conserving as much energy as he can. Unfortunately, his peaceful days come to an end when his older sister, Tomoe, forces him to save the memberless Classics Club from disbandment. Luckily, Oreki's predicament seems to be over when he heads to the clubroom and discovers that his fellow first-year, Eru Chitanda, has already become a member. However, despite his obligation being fulfilled, Oreki finds himself entangled by Chitanda's curious and bubbly personality, soon joining the club of his own volition. Hyouka follows the four members of the Classics Club—including Oreki's friends Satoshi Fukube and Mayaka Ibara—as they, driven by Chitanda's insatiable curiosity, solve the trivial yet intriguing mysteries that permeate their daily lives.

The aloof protagonist: a bookworm who is deeply detached from the world he resides in. He has no interest in others and is firmly convinced that nobody has any interest in him either. His story begins when he stumbles across a handwritten book, titled Living with Dying. He soon identifies it as a secret diary belonging to his popular, bubbly classmate Sakura Yamauchi. She then confides in him about the pancreatic disease she is suffering from and that her time left is finite. Only her family knows about her terminal illness; not even her best friends are aware. Despite this revelation, he shows zero sympathy for her plight, but caught in the waves of Sakura's persistent buoyancy, he eventually concedes to accompanying her for her remaining days. As the pair of polar opposites interact, their connection strengthens, interweaving through their choices made with each passing day. Her apparent nonchalance and unpredictability disrupts the protagonist's impassive flow of life, gradually opening his heart as he discovers and embraces the true meaning of living.

Having slept through all four of her alarms, the energetic Narumi Momose finds herself running late for her first day of work at a new office. As she races to catch her train, she makes a promise to herself that none of her coworkers will find out about her dark secret: that she is an otaku and a fujoshi. Her plan goes instantly awry, though, when she runs into Hirotaka Nifuji, an old friend from middle school. Although she tries to keep her secret by inviting him out for drinks after work, her cover is blown when he casually asks her whether or not she will be attending the upcoming Summer Comiket. Luckily for her, the only witnesses—Hanako Koyanagi and Tarou Kabakura—are otaku as well. Later that night, the pair go out for drinks so that they can catch up after all the years apart. After Narumi complains about her previous boyfriend breaking up with her because he refused to date a fujoshi, Hirotaka suggests that she try dating a fellow otaku, specifically himself. He makes a solemn promise to always be there for her, to support her, and to help her farm for rare drops in Monster Hunter. Blown away by the proposal, Narumi agrees immediately. Thus the two otaku start dating, and their adorably awkward romance begins.