A cheating woman has been forced to pay compensation to a man for having sex with his wife.
Tokyo District Court ordered the unnamed 37-year-old woman had to pay out 110,000 yen (£725) at a hearing on February 16.
The rare court ruling recognised that extramarital sex between same-sex partners is infidelity under the law.
The husband, 39, had filed a lawsuit against his 35-year-old wife’s lover in relation to the affair after the pair met online.
The accused argued that her actions didn’t break up the marriage and so did not constitute infidelity.
But the court ruled the affair had undermined the peace, reports Asahi.
The ruling reflects the changing attitude towards same sex adultery in Japanese law.
It comes after the Tokyo High Court in March last year ordered a woman to pay compensation to her female partner after cheating on her.
In doing so it recognised a same-sex union should be treated like a marriage in law.
The couple had lived together for seven years, married in the US and had discussed having children together.
The judge ordered the accused to pay the complainant damages of 1.1 million yen (£7265.18), reports Pink News.
“It was a relationship equivalent to that in which a man and woman come together to lead their lives in cooperation as a married couple,” judge Hitomi Akiyoshi said.
“A same-sex couple is an agreement between two people, and on that basis, it can be said that it bears the same obligations to fidelity that a legally married couple of opposite genders undertakes.”
Japan remains the only country within the G7 not to legally recognise same-sex couples at all.
This month, the Sapporo district court ruled that the government’s non-recognition of same-sex marriage is unconstitutional.