Koyuki Higashi is slim, articulate and intelligent, things that make a would-be wife attractive to many in Japan. But Higashi knows she will probably never marry because she is a lesbian.

Despite the increasing tolerance of gay marriage in much of the developed world, especially in Europe, and a gradual acceptance of the issue in more liberal states in the US, the subject is not on the radar in Japan or in many parts of Asia.

But when Barack Obama gingerly put his head above the election year parapet, announcing he was in favour of same-sex marriage, it lit a spark of hope on the other side of the Pacific in conservative Japan. "Seeing the US president expressing his support for same-sex couples was like being told it was ok to be who we are," said Higashi, 27.

"Everyone now knows Obama supports same-sex marriage. The impact is so big, it's incomparable." Her partner, 34-year-old Hiroko, who uses only one name, agreed.

"I was really happy to see Obama use his starpower in that way," she said.

Obama's pronouncement was preceded by a global campaign aimed at encouraging a stronger voice for gay rights.