Detective Conan Episode 406 -

Ran, watching, has tears in her eyes. Conan, however, remains stoic but somber. He concludes: "The locket was supposed to be a memento of atonement, but it became a motive for murder. A coincidence of timing and hidden truths."

She provides a photograph of her husband—a handsome man in his early thirties with a confident smile. She also mentions that he was wearing a distinctive silver locket around his neck, which he never took off. Inside the locket is a small, old photograph of a young girl, not her. When Kogoro asks about this, Yukie looks down sadly and says, "He never told me who she was. He said it was a memento of a promise he made a long time ago."

Yukie explains the circumstances of her husband’s disappearance. Three days ago, Keisuke left their home in the morning saying he was going to visit a construction site in the neighboring city. He took his car. He never returned, and his phone has been turned off since that afternoon. The police tracked his car’s GPS, but the signal was lost in a remote mountainous area on the outskirts of town. Detective Conan Episode 406

Kogoro, intrigued by the mystery of the locket and the disappearance, agrees to take the case. Conan, however, is already suspicious, noticing a slight hesitation in Yukie’s eyes whenever she mentions the locket.

Kogoro inspects the car. There are no signs of a struggle—no blood, no torn fabric. The keys are still in the ignition. In the back seat, they find a briefcase containing architectural blueprints and a lunchbox that has begun to spoil. However, something is missing: the silver locket. Yukie had specifically mentioned it, but it’s not in the car or on the ground around it. Ran, watching, has tears in her eyes

Yukie is arrested. As she is led away, she looks at Ran and says, "Tell him... tell my husband... I’m sorry we couldn’t keep the promise of the locket." It’s unclear if she means the promise to forget the past or the promise of their marriage.

This episode is an anime-original story (filler) that aired on June 13, 2005. It is a single-episode case featuring Conan, Ran, and Kogoro Mouri. Opening Scene: The Afternoon at the Mouri Detective Agency A coincidence of timing and hidden truths

The main suspect becomes Yukie Sonoda herself. But she has a solid alibi: she was at a friend’s house for tea from 1:00 PM to 5:00 PM that day, and then at a supermarket (recorded by security cameras) from 6:00 PM to 7:30 PM. She couldn’t have driven to the mountain, killed him, and returned in that timeframe.

He explains: Ten years ago, Keisuke Sonoda caused an accident that killed Miyuki, Yukie’s sister. Keisuke was never criminally charged due to a lack of evidence that he was driving, but civilly, he paid a large settlement. He later met Yukie, who apparently did not know his connection to her sister’s death. They married.