Written Japanese also includes a pair of syllabaries known as kana, derived by simplifying Chinese characters selected to represent syllables of Japanese. The syllabaries differ because they sometimes selected different characters for a syllable, and because they used different strategies to reduce these characters for easy writing: the angular katakana were obtained by selecting a part of each character, while hiragana were derived from the cursive forms of whole characters. Modern Japanese writing uses a composite system, using kanji for word stems, hiragana for inflexional endings and grammatical words, and katakana to transcribe non-Chinese loanwords as well as serve as a method to emphasize native words (similar to how italics are used in Romance languages).
Why do the syllabaries differ?
they sometimes selected different characters for a syllable