Its easy to bypass the captcha. The bot uses a driver that hooks directly to the client and it knows where each NUMBERS are located even without using OCR.
Also, there's no bots in Japan because they restrict IP registrations and when found out you're playing outside Japan, you get Banned. Even if you speak English sometimes and players reports you. You get banned, well not everyone I guess but Happened to me. lol.
Well, Japan is as good as dead too.
BOTS comes to a game that is popular.
Give it time, bots will flood BDO too, even TOS. ;P