The Detective Boys are filming a documentary under Ayumi's direction about a serial vandalism case that Kogoro seemingly solved by chance. Unknown individuals defaced shops in Beika City with the mysterious graffiti "MIRUNA" and destroyed surveillance cameras. Kogoro recounts how he caught the culprit, fitness enthusiast blogger Miki Kohei, in the act at night. However, Conan discovers inconsistencies: Miki's physical deterioration and apathetic statements suggest outside influence.

Ayumi's illustrated diary, which maps the crime scenes, reveals a pattern: The vandalized shops surround the highly secured Kaneko Jewelry Store. Conan realizes that the attacks deliberately disabled cameras to prepare for a robbery. The true mastermind is Inukai Aoi, owner of a sweetshop and former hypnotherapist. She manipulated Miki using an IoT planetarium to remotely control him.

Inukai, herself a victim of the vandalism, staged the acts to divert attention from the planned jewel heist. The Detective Boys confront her at the jewelry store when she—after Miki's arrest—attempts the robbery herself. The case ends with the exposure of the hypnosis scheme and the rescue of the documentary, which, despite initial doubts, becomes a success.

A preview of the next episode hints at a mystery involving a gold coin and a fire in a traditional house.