Y-san Disappearance Involving Katagiri Shu, Obihiro, Hokkaido, Japan
This source-based behavioral analysis does not establish a clinical diagnosis, motive, or legal finding.
The source describes a concealed affair that reportedly shifted into separation conflict, repeated contact, financial demands, threats, fear of exposure, and a disputed fatal encounter. The behavioral account supports analysis of relationship stress and escalation but does not establish clinical diagnoses or prove the motives attributed by the narrator.
Y-san and Katagiri were both married teachers whose affair began in a shared workplace. The source reports that Katagiri later attempted to withdraw while Y-san continued contacting him and appearing before him, creating an unstable pursuit-and-avoidance dynamic. Alleged money demands and threats involving his wife and child intensified the conflict, while secrecy limited outside intervention.
The reported pathway moved from secret workplace infidelity to attempted separation, persistent contact, financial and threat-related conflict, an early-morning meeting, a disputed joint-suicide plan, Y-san's death, concealment, and evidence destruction. The source distinguishes reported facts from speculation about intent and emotional states.
Each entry separates the reported behavior or state from the analytical strength of the available narration.
| Behavior / construct | Person / subject | Detailed case context | Evidence |
|---|---|---|---|
| Infidelity or competing attachment Relationship stressor | Y-san and Katagiri Shu |
Y-san reportedly initiated the affair while both she and Katagiri were married. Katagiri's wife later had a child, while the affair continued and became increasingly incompatible with his family relationship. The competing attachments created secrecy and pressure around any attempt to end the affair. Context or trigger: Both participants were married teachers when their workplace relationship developed into an affair in 2018. Reported expression: The source describes a concealed romantic relationship overlapping both marriages. The affair became the central context for later separation, financial conflict, threats, and the fatal encounter. |
Explicitly reported Confidence: High |
| Separation or abandonment threat Loss or threat | Y-san and Katagiri Shu |
Katagiri's attempt to end the relationship appears to have become a major destabilizing event. Y-san's reported refusal to accept the breakup and his reported avoidance created a cycle in which separation was repeatedly attempted but not achieved. This is a relationship-stressor interpretation, not a clinical finding. Context or trigger: Katagiri reportedly wanted to end the affair beginning in 2019 and attempted to create distance after a school transfer. Reported expression: The source reports that he withheld his new address and avoided contact, while Y-san continued reaching out and appeared before him. |
Narrative-supported psychological state Confidence: High |
| Deception or concealment Behavioral pattern | Katagiri Shu OffenderLover of victim |
The source presents concealment at multiple stages: the affair was hidden, Katagiri allegedly used a false explanation to leave his car at school, and he later destroyed Y-san's smartphone and vehicle document. These behaviors may indicate efforts to manage exposure and investigators' understanding, although the supplied material does not establish every intention. Context or trigger: The affair overlapped his marriage, and the source says he initially told Y-san he would divorce but did not intend to do so. Reported expression: He reportedly concealed his new address, avoided contact, lied about remaining work, and later burned personal items after burying Y-san. |
Narrative-supported psychological state Confidence: High |
| Financial strain or dependence Relationship stressor | Y-san and Katagiri Shu |
The reported financial exchanges transformed the relationship conflict into a material dependency and leverage issue. The source portrays the payments as part of an escalating breakup dispute rather than ordinary relationship support. The figures and demands are source-reported and are not independently verified in the supplied material. Context or trigger: The source reports that after Katagiri sought to end the affair, Y-san demanded large payments connected to the breakup. Reported expression: Katagiri reportedly paid three million yen and then four million yen, while the source says demands and phone calls continued. |
Explicitly reported Confidence: Moderate |
| Fear or perceived threat Emotional state | Katagiri Shu OffenderLover of victim |
Katagiri's stated explanation emphasizes perceived danger and entrapment rather than anger alone. The source also acknowledges that this account may have been incomplete or self-serving, especially because he survived the alleged joint-suicide act and continued ordinary work afterward. Fear is therefore a reported subjective state, not an established justification or causal conclusion. Context or trigger: Katagiri reportedly faced continued contact, financial demands, alleged threats, and fear that the affair would expose or damage his family. Reported expression: He told the court that he wanted to escape from Y-san, and the source describes his claimed fear as increasing after the breakup attempts. |
Explicitly reported Confidence: Moderate |
| Premeditation and planning Planning or impulsivity | Katagiri Shu OffenderLover of victim |
The reported transport, burial, and burning of items show organized post-incident behavior. They do not by themselves prove that Katagiri planned the killing before the meeting. The source explicitly preserves uncertainty about whether the fatal act was premeditated or arose within the disputed joint-suicide scenario. Context or trigger: After Y-san's death, the source reports body transport, burial with a shovel, and burning of personal items. Reported expression: The sequence involved multiple post-incident actions across the day, although the source says advance planning to kill Y-san was not established. |
Narrative-supported psychological state Confidence: High |
| Staging or evidence concealment Post-offense behavior | Katagiri Shu OffenderLover of victim |
Burning the smartphone and vehicle document is consistent with an attempt to conceal evidence or reduce traceable links after the death. The source treats it as evidence destruction, while the psychological meaning beyond that behavior cannot be assessed confidently. This observation concerns reported conduct and does not independently establish legal intent. Context or trigger: After burying Y-san, Katagiri reportedly burned her smartphone and vehicle inspection certificate. Reported expression: The reported conduct was directed toward removing or destroying items connected to Y-san and the incident. |
Narrative-supported psychological state Confidence: High |
Select a stage to expand it; scroll horizontally to follow the full sequence.
The source reports that the two married teachers developed an affair after working at the same school. The relationship created an overlapping attachment structure in which both participants remained connected to their spouses.
By 2019, Katagiri reportedly wanted to end the affair. The later school transfer and his withholding of his new address were described as efforts to create distance, but the source says Y-san continued to contact him.
The source reports that breakup-related demands grew to millions of yen and that repeated phone calls continued after payments. This added financial leverage to an already unstable separation process.
The report says Y-san threatened Katagiri's wife and baby if he did not divorce. Whether or not the threat was ultimately substantiated, it was presented as a point at which the conflict expanded beyond the two affair partners.
Y-san appeared at Katagiri's practice game and later met him outside his home during the early morning. They then traveled together to a parking area, where the reported joint-suicide proposal was made.
The source reports that seatbelts were placed around both participants' necks and that Y-san died from neck compression while Katagiri survived. The exact intent and degree of planning remain disputed, so the behavioral classification cannot be treated as definitive.
Katagiri reportedly transported and buried Y-san's body, attended work, and later burned her smartphone and vehicle document. These actions formed the post-incident conduct that led investigators toward the burial site and evidence-destruction account.
At trial, Katagiri maintained that he believed Y-san consented to a joint suicide and said he wanted to escape from her. The court imposed a six-year-and-six-month sentence, but the supplied report states that the exact events inside the car and Katagiri's advance intent could not be fully established.
Arrows show the sequence described in the source narrative; they do not prove that one psychological state caused the next event.
The material is a narrated video report rather than a complete court record. Several psychological interpretations are explicitly speculative, and the exact events inside the vehicle, Y-san's intent, and Katagiri's advance planning remain unclear. No professional psychological diagnosis is reported for either central participant.