Why the readings of Japanese characters can be such a mess

The core of the Japanese writing system, called kanji, comprises Chinese characters imported many centuries ago.

In Chinese, each character only has one reading. In Japanese, however, each of those characters usually has at least two readings. But it's easy to think of characters that have four readings. And I'm sure there are those with even more, but I can't think of one off the top of my head.

So why so many readings? Because each character tends to have more than one:

1) Japanese readings. The Japanese reading is the "native Japanese" word that expresses the concept described by the Chinese character.

2) Chinese readings. Why is it that the word only has one pronunciation back in China, but it's ended up having multiple Chinese readings in Japan? Because different pronunciations have gotten imported from different regions and eras of China.

Add to this the bonus of "ateji," whereby Japanese occasionally assign an arbitrary pronunication to a kanji or kanji compound. (This is like me telling you that my name is spelled "Stephanie," but please pronounce it "George.")

For a Japanese native, or a highly proficient foreign reader, none of this causes that much difficulty. The combinations of rules and rote memorizations burn their way into your brain after a while. But for the beginning Japanese-language student, it makes things pretty nutty.