I am in exactly the same situation (British south asian) as you are and would be interested to see how you get on. I was planning a 2 week trip to Japan for a mix of tourist stuff and some occasional punts and cross off a Japanese girl from my list. I have lived and punted in most of the Fareast without much difficulty.
Unfortunately Indian Indians are giving us all a bit of a bad rep, especially in Thailand. Not so much in Indonesia, Malaysia, Vietnam etc. yet. On a more positive note, in Thailand in the last couple of years I have noticed things are improving somewhat and the girls can distinguish better from sandal wearing, loud and proud hand holding brigade. The richer class of Indians who are not arriving on coaches also tend to spend money.
Anyway after much wrestling, I bottled it and decided to stick to what I know and go to Thailand and Hong Kong. I also thought I perhaps have better odds of landing a Japanese girl in Hong Kong, but if not there is a variety of other nationalities to trawl through without much difficulty.
However, in the course of my research I did come across the 'Japanese Hentai Girls Collective' (google for their website and YouTube videos). I did contact them over line and explained my predicament. I was assured that, yes, it may be a consideration for some of the girls but not all.
I found the agency to be very professional and communicative. I was advised to stay in the Shinjuku area, where most of the girls are located. Other options would be to go to Osaka and visit the walk-up red light areas there like Tobita Shinch (lots of youtube videos online) where you can see the girls and they will indicate there and then if they have any interest.
You can also try the Tokyo Hentai Club and see who is available.
Other advice is just to be well groomed, dress smartly, not have a pot belly or wear sandals or hold your male friends hands while walking down the street, and you should hopefully do fine. Good luck!
