I'm native Chinese, Mandarin speaker, & I love Japanese, too.
Japanese derives from Classical Chinese (Ancient Chinese), in fact, Kanji, Hiragana, Katakana, are all created based on Chinese characters (regular script, cursive script, or transformative style), but in terms of grammar, Chinese (Mandarin) is, as a whole, very different from Japanese. & I guess that, Japanese might be a little easier than Mandarin for Western learners. & I hope the information can help you decide between them.