A 55-year-old part-time computer science lecturer resigned from Taisho University in Tokyo on Thursday after being found naked in a corridor.
The man had stripped amid a row with his 21-year-old lover, a student with whom he lived, a university official said.
The woman had told him: “Get naked if you want me to believe you.”
He did, whereupon she grabbed his clothes and fled.
“It was clear that the student was mentally unstable,” said Masahiro Kashiwagi, head of the university’s administration office.
Kashiwagi said the school had spoken to both people involved and decided not to identify them. He added that the pair had been living together with the consent of the student’s parents.
The man had taught computer classes for more than a decade. He submitted a letter of resignation Thursday, which the university accepted.
Kashiwagi said the university “sympathized with the instructor to some extent” but decided he should “take responsibility for what he did, which deviates from standards of decency and poses a threat to public order.”
The university is taking no action against the student, who is in her final year and is scheduled to graduate in March.
“We told the student that she needs proper medical treatment, and that she should try to lead a happy life with the man,” Kashiwagi said.
The incident occurred at around 3 p.m. when a student found the man standing naked in a passageway connecting two buildings and reported it to the administration office, a university official said.
A staff member raced to the scene and found that the man was a lecturer.
The university website carried a message by the man to students stating he “deeply regrets what happened,” and he apologized for causing “considerable trouble and anxiety.”
“Although it was something that I did in order to protect someone close to my heart, I apologize for its resulting in such an incident,” he said.
The man said the student “tends to get emotional and act irrationally,” adding that whenever she gets agitated and makes demands he complies to calm her down.