I found PART of the Japanese language easier to learn after studying Chinese.
Japanese has two basic strains, an "indigenous" strain, which its own hiragana and katagana script, and the "Chinese" based strain, in which the Japanese adopted the Chinese Hanzi as "Kanji" for many words, as well as a pronunciation similar to the Chinese for those words.
(Nearly) all Chinese Hanzi is part of the Japanese language, so someone with a knowledge of Chinese would be understood writing Hanzi. But it would be hard for the Chinese person to read (and hear) the non-Chinese part of the language, written in katagana and hiragana.
It's like saying that English has two strains, a Latin strain and a Germanic strain, and therefore, two words, e.g. "chair" and "stool," for many words. "Chair" comes from the French "chaise" and "stool" from the German "Stuhl." It's like saying that a French or German speaker could understand all the French/German derived words in the English language, and with some knowledge of English, could be understood using those words of his/her language that is part of English.