There is a simple tips to enable the emoji keyboard on your iPhone. You can now use these little japanese icons. Note that you can delete this app if you don’t want to keep it. Your Emoji keyboard will still be activated.

Step 1: Install Spell Number from the App Store which is a free apps. You can install from direct iTunes link here.

Step 2: Launch the app and type 91929394.59

Step 3: Press the "Home" button

Step 4: Go to Settings > General > Keyboards, and under “Japanese” select “Emoji”