There are some great Japanese affiliate programs that have tube content in their offer:
JAV HD contains HD, tube in following niches:
Straight: Editor's Choice, Hairy, Hardcore, Toys
Ethnics: Japanese
Fetish:
Program:
JAV Bucks (21 sites, NATS). Revenue: 60%
Pay method: check, wire, Paxum
Promo:
Photo FHG (50), Flash FHG (50), Tube clips (15)
Osaka Schoolgirls in following niches:
Straight: Hardcore
Ethnics: Japanese
Program:
Stand Ahead (18 sites, NATS). Revenue: 60%, $30 PPS
Pay method: check, wire, Paxum
Promo:
Video FHG (224), Tube clips (230)
Tokyo Group Sex contains HD in following niches:
Straight: Hardcore, Asian, Gangbang
Ethnics: Asian, Japanese
Program:
Payserve (57 sites, in-house script, VXSBill). Revenue: 50%
Pay method: check, wire, Paxum, CashX
Promo:
Photo FHG (5), Video FHG (23), Tube clips (1)
You can check out other 150 Japanese affiliate paysites listed bellow. I'm sure you can find some really nice content for your tubes here:
Japanese Sponsors @ SignBucks.com
Feel free to use options in the right sidebar, like "tube" or "tube clips". That will be of help when searching for appropriate programs.