To type like a real Japanese person you may need animated emoticons. Ones that blink, and flash and what not like the ones on Tanaka Reina's Blog. You may also need to actually know Japanese. However these emoticons are a good way to start.
Step 1: Active the Japanese keyboard on your iOS device
-Go to Settings, General, Keyboard, International Keyboards.
-Add New Keyboard, Japanese(Kana)
Step 2: When the keyboard is in use switch between languages by touching the globe symbol
Step 3: Open The emoticon section ( The "^_^" button )
Step 4: Begin expressing your situation and emotions through complex emoticons