Hello, I'm M&N's mommy.

We recently installed a doggy door for the troublemakers to have easy access to their bathroom (our back yard). I had already taught Mika how to use the door when I took him on the 1 week vacation earlier this year. I had trouble with little Nami-chan though. I couldn't figure out if it was the noise of the magnet catching the metal or the flap coming down that scared her. (I brought her to a local pet store to let her explore after her check up with the vet, and on the way out, she thought that the middle partition for the two french doors was a way out, so she walked right into it.) [Nami: MOOOOOOOOOOOOOM... why do you have to share that story?] Anywho, I'm not sure if that bonk on the head with the glass spooked her so she wouldn't go through the dog door with the flap down, or what.
We made her feel comfortable around the door, whenever she approached it to sniff it, we gave her a treat and a "good girl, Nami," then I open the flap and put a treat on the other side of the door (the side where she should walk to) and she hesitantly stuck her nose in, sniffed to make sure that it wasn't a trick, and quickly grabbed the treat and retreated. M&N's daddy and I did that drill for an hour total (there were times when she wasn't interested at all in it, so we took a short break) slowly moving the treat back further so she would have to go further through the door to get the treat, but she would not put her back feet through the door. We stopped there that night as she wasn't interested in the treats (or toys I tried to lure her to put her back feet in with) and the door anymore and called it a night. I planned to resume the exercises the next day, but when I woke up the next morning (Their daddy put them outside just incase Nami didn't know how to use the dog door) and started the washer, I heard the dog door close. I assumed that it was Mika, because he was going in and out of the door right after it was installed, but when I looked down, there Nami was sitting and looking up at me with the "whatcha doing?" face.
Oh, I forgot to mention that I walked the whole downstairs to make sure nothing of ours was destroyed by the ferocious Nami teeth (Did I mention she loves to chew on things?) and no canine was inside of the house.
Boy was I surprised when I saw Nami at my feet. I walked to the living room and Nami followed me and I saw that Mika was still outside and was looking in to see what we were doing. Then, I see Nami approach the dog door, paw at it, so the flap would open a little a couple of times (I think she's making sure that she won't bonk her head again.) then slowly and cautiously put her head through, then her two front paws, then slowly inch through until she was fully outside. YATTA!!! She did it! I was so proud of her when she went through.
I stayed with them for a while longer before heading to my office/work room to make sure it wasn't just a two time deal. It wasn't! Nami snuck back in right behind me as I was entering the kitchen sliding door (what a cheater), went to her stash of chews on her bed, took one, then tried to go out of the door. She got discouraged because the chew kept hitting the side of the door, so she went to the kitchen sliding door again where I used my body (mostly legs, they're too small for body blocking unless I'm sitting on the floor) to block her from the door. After a few tries of getting to the kitchen sliding door, she gave up and went back to her dog door. She whined a couple of times while sitting in front of the dog door, but then she got together enough courage to try again (without my help, I was a good 10 feet away watching what she would do) and this time, she did it! She made it out of the doggy door with her chew in mouth (then proceeded to play keep away with Mika, I think as her way of showing him that she managed to bring a chew outside through the dog door all on her own).
Now, what I wonder is, who taught Nami to put her back paws through the door. M&N's daddy and I know that we only got her part way through. The only other inhabitant of our property that could have taught her was Mika. I think with enough of him going in and out of the door, she got her courage up to try it. Either that, or the shiba talked to each other and Mika told her in shiba language how to go in and out of the door. (And now, I bet you, she thinks this is the best thing ever invented. No more waiting at the door for someone to open it.)
Note: The picture of the dog door is from the Petco site. Petco is where we bought the dog door. The dog door works, but install was a pain in the neck. If you're looking for a dog door and don't want a difficult install, don't buy the Petsafe one from Petco. Look for a different brand at a different pet store, or go to Home Depot. Home Depot has a different brand dog door, and it might be easier to install, I don't know though, I couldn't bring the box down to look at the other side of the box for more information.