High school student Tsunemi Kousuke has a habit of overthinking everything. One morning, he finds a notebook in an empty classroom covered in strange symbols. After puzzling over them, he realizes the marks are a cipher, and he deciphers them to reveal the name of his quiet, seemingly demure classmate, Tojino Airika. It turns out the notebook was left deliberately. Tojino, far from the reserved girl she appears to be, is a fanatical escape room enthusiast, and she has been looking for a partner. She immediately ropes Tsunemi into a homemade escape game she has set up in the old school building. He manages to escape by relying on his tendency to think things through, and the two of them become unlikely escape game partners.

The story follows Tsunemi and Tojino as they tackle a variety of escape games, from simple classroom puzzles to large-scale events supervised by the real-world escape room company SCRAP. Each chapter typically presents a new puzzle for the characters to solve, and readers are invited to solve along with them. As they work together, Tsunemi begins to see past Tojino's quiet exterior and grows to appreciate her intense passion, while she comes to value his careful, methodical approach. Their partnership gradually deepens into friendship and then into something more.

A major arc in the story deals with Tojino's past. She lost friends in middle school because her obsession with escape games led her to play solo and shut others out. She reconnects with her former friends, including the silver-haired Shirakawa Kiki and the stoic Nekoyama Othello, and with Tsunemi's help, she confronts and overcomes the guilt she has been carrying. This allows her to open up more fully.

In the climactic arc, Tsunemi decides to confess his feelings in a way that honors their shared passion. Despite having no artistic talent, he designs and builds his own original escape game, enlisting the help of their friends. Tojino plays through the game, solving the puzzles he has crafted, and in the end, she understands his feelings. The story concludes with the two of them becoming a couple, surrounded by their friends, with the promise of many more escape games to come.