Rivers has been interested in Japanese culture (and Oriental culture in general--I mean, have you listened to Pinkerton? And he did marry a Japanese woman in 2006...) for decades so it comes as no surprise whatsoever that he's released a Japanese language album.
What is surprising--and shame on me--is that I hadn't heard about this record at all even though it's been out in Japan since March. Then again, it was a Japan-only release--and it was released under the name Scott & Rivers, the "Scott" being Scott Murphy of the band Allister.
The album is finally available domestically through iTunes. Exclaim has the story of the record here. A full tracklising follows this video for the first single, "Homely Girl."