Technique 1: Get missions by VPN / Creating Japan Gmail account / Hola Application.

Create a Japan Gmail account and simply use Hola VPN application to do all the missions.
You can divide it into 3 simple steps (and once you do that, you will only need to do step 3 to download the missions): 

1. Create a Japanese Gmail account and link it to your google play (by using Japan VPN the first time)
2. Install Hola application and link the applications which are needed.
3. Download the missions.

1. Create a Japanese Gmail account:

Sign up at: https://accounts.google.com/SignUp?service=mail&hl=ja&continue=http%3A%2F%2Fmail.google.com%2Fmail%2F%3Fpc%3Dtopnav-about-ja

a) Fill up the form. (Name, surname, Email, password, birth date, Gender and validate)

b) Just click on the blue button

c) Close the pop-up

d) Your japanese Gmail account has been created.

Now let's link the Gmail account to our phone.

e) Connect to your vpn. Connect to Nah VPN

f) Select Japan

g) Select any VPN number

h) Accept.

i) Connect.

j) Tick and validate

k) you are connected.

l) Open your phone setting.

m) Select Account - Add account.

n) Select Google

o) Select Existing

p) Enter your created japanese Gmail account.

q) OKAY

r) No need to create a Google+ account. SKIP, SKIP, SKIP

s) Just synchronize with what is useful: App Data, Gmail and Internet.

t) Now open Playstore (always with your VPN to Japan opened).

u) Change your account.

v) Congratulations!!! Now your google play is on Japan Country!

2. Hola application: (We are almost done!!!! Don't give up!!!)

Download and install it from: https://play.google.com/store/apps/details?id=org.hola&hl=en

a) Open Hola Free VPN application.

b) Click on My Apps.

c) Select the following applications and change the country to Japan : 

Browser,

 Internet Explorer, 

Jap App, 

Google Play Store.

To change them, DON'T CLICK ON "Open"!!!! JUST CLICK ON THE ICONS!!!

Do the same for all enlisted applications above.

3. Download missions from Japanese Application (Final step!!!!

That's the last sprint!!!)

a) Open Jap app.

b) Select coins icon.

c) Select the first tab and any mission.

Here I chose 755 application.

d) Validate.

e) Now it sends us to Playstore japanese version, you can download as normally.

f) Accept.

g) Open.

h) The application starts... just wait 30 sec (sometimes you need to register to get the coins, just do by instinct).

i) Here you got your coins! 

Good news to end up this tutorial: You can now close your VPN (Nah VPN) and that everytime you use the Jap App, you will be able to download at normal speed thanks to Hola Application!!!! 

Special thanks to Gremlin for his help!!!