Answer:
Japanese does not have an alphabet. It has 2 syllabaries and it also uses Chinese characters.
There are 204 "Letters" in the Hiragana and Katakana, which are syllabaries, not alphabets. (Each character in the syllabary respresents a whole syllable, not a letter).
The number of Kanji, or Chinese Characters is debatable, as upwards of 70,000 characters. But only about 2000 are officially used.
Also the Arabic Numerals are used ( 0-9 in symbol form), and Latin letters are sometimes used.