STEPS
TOOLS
Go to settings
Go to general
Keyboard
Add a new keyboard
Scroll down to Japanese romaji
Click the Japanese word looking thing XD
Click 123 then the face in the corner
This will pop up so click the arrow in the corner
A bunch of these will pop up so you can click on any of them ( they are little faces and stuff) and enjoy!
If you have any questions please comment :P
 iPhone 

How to install japanese romaji

Install Japanese Romaji