In case you haven't noticed, Japan uses characters (Kanji) that pictorially describe an item, concept or idea.I can't actually believe an entire country uses smiley faces/little pictures to communicate!
They are a pictorial based culture when it comes to expressing their ideas.
In fact, when conversing in Japanese, you may see Japanese folks using their hands to illustrate specific Kanji (or Hiragana/Katagana) to clarify meaning.
So there is no doubt, that as a culture, they rely on Emoji to communicate.
If Apple wants to be a player in the Japanese market, they need Emoji. It's as simple as that.