I would try (if you already haven't) crate training. Most dogs will not go in a crate and actually enjoy the break away (mine actually will go in to take a nap).
Other tips would be to establish a routine & use praise... I usually start out with letting the dogs out the front door as soon as I wake up, (you can use a code word or simply give a lot of praise for going outside) they are then let out in the afternoon, after they eat, and then again before bed time. If they do need to go out again they will usually paw at the door and we know this is the signal that they have to go. We have done this with all of our dogs since they were 3 months and it has worked out well. Good luck!
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I agree with the crate training... our akita was house broken by the time of us having him for 3 weeks... and all we did was start with the crate training... and him to will use his crate to sleep that is if the couches aren't available :)
I've seen a look in dogs' eyes, a quickly vanishing look of amazed contempt, and I am convinced that basically dogs think humans are nuts." - John Steinbeck
I would also suggest a crate, they are surely beautiful dogs, and this is one breed that CANNOT be outside. (not that any dog deserves to be outside at all) They are suseptible to bloat, the hot temps are not good for them, and the cold temps are not good for them either, very high matinance breed.CRATE!