When you're typing a message, pick the Japanese keyboard by holding down on the globe icon. Then, pick the smiley face in the lower left-hand corner. Swipe left and right on the suggestions bar ...

In some apps, it'll add an emoji smiley icon in the lower right. If you've got an older Android device, you can download the Android KitKat keyboard APK to get KitKat's keyboard. To do that ...