First of all, are you talking about the
languages, which are what you actually speak and hear (even if only in your head), or the writing systems, which are what is printed on a page? Things can get confusing if you don't distinguish those.
You really can't call the Japanese language "Chinese-based", since the Chinese and Japanese languages are not at all similar. It's true that Japan has borrowed a lot of words from Chinese, but other features of the languages, like grammar and pronunciation, are extremely different, and the two languages have different origins. Of course, neither language is at all like Latin or its descendant languages.
As for the writing systems, the Japanese writing system was based on the Chinese one and is still pretty close to it, though it's not identical. The Chinese writing system is of a type called "logographic" (
http://en.wikipedia.org/wiki/Logogram), meaning that each character stands for a word or a major part of a word. Japanese kanji characters are directly borrowed from Chinese characters (known in Chinese as "hanzi").
Japanese also has two other sets of characters, hiragana and katakana (collectively known as "kana"). These characters stand for syllables (usually either a consonant followed by a vowel or a simple bare vowel), so while they are not an alphabet, they are a bit closer to one than the kanji are. This sort of character set is called a "syllabary" (
http://en.wikipedia.org/wiki/Syllabary).
And finally, there are alphabetic writing systems like the Latin alphabet. Of course, you can have an alphabetic writing system that doesn't use the Latin alphabet: the Greek, Cyrillic, and Hebrew alphabets are obvious examples. And using the Latin alphabet doesn't mean your
language is Latin-based. Italian, Spanish, and French are Latin-based languages (they all descended from Latin) which also use the Latin alphabet. English, Czech, and Vietnamese use the Latin alphabet, but none of these languages are Latin-based (even though English has borrowed lots of Latin words).
I know that's a lot of detail and makes things more complicated, but I hope it also clears up some confusion.
