Ambassador Koro Bessho said recent elections have put both Japan and South Korea "in a better position to talk about" their strained relations, Yonhap News Agency reported.
"So, I am optimistic that we can try to look for a relationship with a stable future," Bessho told a forum in Seoul.
Relations between the countries have been edgy for some time. South Korea has been angered by Japan's refusal to apologize for kidnapping South Korean women during World War II and forcing them to act as prostitutes for Japanese soldiers during World War II.
Outgoing South Korean President Lee Myung-bak added to the stress last August when he visited the Dokdo Islands, which both South Korea and Japan have long claimed.
The ambassador hinted Japan may be softening its attitude about apologizing for forcing women into sexual slavery.
"I can say that Japanese prime ministers have acknowledged that, during the past, Japan has caused tremendous damages and sufferings, especially in Asia, and the government of Japan is squarely facing historical facts and expresses feelings of deep remorse," Bessho told the forum. "And that is something that [Japanese] Prime Minister [Shinzo] Abe has shared."