The Detective Boys are commissioned by a classmate to find his missing cat, Akira. When they do finally find Akira, the cat has just emerged from a house's window, covered in blood. The Detective Boys immediately investigate, and see a bloody corpse face-down in the house's bathtub.
Murder
Location:Tanaka household
Suspects:Tomofumi Tanaka
They call the police, and Inspector Megure arrives with a squad to investigate. The elder brother, a rough and rude man, lets them into the house but then goes into a room while they search. The soft-spoken younger brother arrives soon after, but is cooperative with the police. However, despite a thorough examination of the entire house, no corpse is found. Inspector Megure believes that the Detective Boys were playing a prank and the police leave, to Conan's frustration.
When the Tomofumi arrives home, a small leaf falls out from his slipper.
While the police are there, Tomofumi abruptly answers the phone when it does not ring audibly, only with a flashing light.
The tree outside the room where Kazuyoshi was sleeping leads to a culvert with a ledge that one person could stand and walk on.
After sunset, the curtains of the room with Kazoyoshi haven't been drawn, and he hasn't moved from the chair.
Resolution
With his Detective Boys Badge transmitting his deductions to the Detective Boys who are on the phone with Inspector Megure, Conan explains that the corpse they saw in the bathtub was actually the body of Kazuyoshi, whom Tomofumi murdered. Between when the kids saw the body and the police arrived, he cleaned the body and set it up in the room as if it were watching TV, then answered the door as his brother. After establishing the presence of Kazuyoshi, he went into the bedroom with corpse and climbed out into the nearby culvert using the tree, sneaking around to re-enter the house as himself. The TV that Kazuyoshi appeared to turn off at Tomofumi's request was set to turn off by timer, rather than remote, and Kazuyoshi's voice was simulated by Tomofumi's voice on the phone's answering machine, which Tomofumi dialed using the cell phone hidden in his pocket.
Motive
Kazuyoshi had been blackmailing Tomofumi to let him freeload there forever and be given more and more money whenever he wanted, or else he would reveal that Tomofumi had been illegally trading stocks. Tomofumi finally snapped at the frustration of being used by the elder brother he had once greatly admired, and killed Kazuyoshi.
