This video will help you set up the JP account (or really any youtube video they're all the same:

The best way to buy the 2k yen codes so you can buy the game are from right here http://www.play-asia.com/playstation-network-card-ticket-1000-yen-for-japanese-network-/13/703xk6 since ape escape 3 costs 1234 yen you need 2 1k yen cards. The code gets emailed to you within 5 minutes of buying them

After setting up a Japanese psn account, and putting in the codes from a Japanese psn card: http://imgur.com/a/EjJUz