“A key but not being able to find the keyhole”

“A key but not being able to find the keyhole” is a recurring metaphor for clues that are real but not yet usable: the detectives have pieces of Seizo Naemura’s past, yet cannot make them open the question of where he went or what happened to him. First voiced as Sakagami’s image of investigative frustration, it later describes Matsumiya’s intuition as well, turning a practical dead end into a figure for knowledge that is present but not yet legible.

The Case Without a Lock

After interviews with former teachers and pupils, the detectives know that Naemura had once been a committed teacher. They have learned little about his more recent life, however, and the former teachers cannot say where he is or what he looks like now. Their accounts reinforce the outline of a person who existed in the school community while leaving the central question of his disappearance untouched.

The obstacles are not simply a lack of effort. Records from the relevant period have vanished, and employment-document retention rules cover only three years for full-time workers, not short-term contractors. In an industry organized through layers of subcontracting, work may be done by people whose identities are difficult to trace; forged residence cards and false names are described as routine. If “Shunichi Watabe” was an assumed name, the search for any trace of him becomes harder still. The detectives have a key in the sense that they possess leads and fragments, but the circumstances around those fragments provide no clear point of entry.

Sakagami’s Image of Frustration

Sakagami gives the metaphor its most explicit investigative meaning. After calling the incident room, he reports that the instructions amount to doing a good job and leaving no stone unturned, but the encouragement does not alter the case’s impasse. Naemura seems to him like a key for which no keyhole can be found: a person and a set of clues are before them, but no connection allows the evidence to turn into an answer. Sakagami fears that the team will return to Tokyo with nothing to show for its work.

The image gathers force because the search has produced information without resolution. The teachers remember Naemura, and one suspects his divorce may have led him to leave his post, but that possibility supplies no specifics. Their inability to assess a sketch of his present appearance further exposes the distance between knowing that Naemura once belonged to the school and locating the man he later became. The metaphor does not mean that there is no key; it names the more frustrating condition of holding something that seems relevant without knowing where, or how, it fits.

A Hunch Before Its Shape

That sense of an absent connection carries into Matsumiya’s private reflections. After recording the day’s interviews on his tablet at the hotel, he cannot shake the feeling that something important is missing. He is frustrated and edgy, convinced that he is failing to notice something directly in front of him, but he cannot yet explain what it is. He briefly wants to call Kaga, then decides against it because he would struggle to describe the feeling and knows Kaga has work of his own.

The next day, the partners divide their inquiries: Matsumiya goes to Biwa Gakuen Orphanage, where Hiromi Asai lived from the middle of her second year of junior high through high-school graduation, while Sakagami heads to Maibara, Naemura’s hometown. As they part, Sakagami hopes that between them they can find some trace of the keyhole. The image has shifted from a complaint about the investigation’s lack of progress into a compact statement of its next objective: searching separate places and histories for the missing connection.

Recognition Between Matsumiya and Kaga

Later, while speaking with Kaga, Matsumiya hears a description of something present but impossible to identify: it is there, right in front of him, but its shape remains indistinct. Matsumiya immediately recognizes the sensation, saying that this is exactly how he feels too. The moment links his private unease to the same problem the keyhole metaphor has already named. His intuition is not yet an answer; it is awareness that the available facts conceal a pattern he cannot make out.

The expression therefore marks both the limits and the persistence of the detectives’ knowledge. They are not empty-handed: interviews, records, identities, and possible explanations have accumulated. Yet those fragments have not found the connection that would make them cohere. When Matsumiya recognizes the feeling in Kaga’s account, the metaphor’s emphasis moves from Sakagami’s fear of returning with nothing to the possibility that an indistinct clue is still waiting to be recognized. The keyhole remains unfound, but the shared recognition makes the gap itself visible.