Italian, French, Spanish, Portuguese, and Romanian are all directly derived from Vulgar Latin. Japanese is a linguistic isolate, perhaps distantly related to Korean (which is also a linguistic isolate). Japanese borrowed the Chinese writing system, and a little bit of vocabulary; calling Japanese a variation of Chinese is akin to saying English and German are a variation of Latin.

It's even further remote than saying English and German are a variation of Latin, as at least the Germanic languages are in the same family of Indo-European languages. Japanese and Chinese are not related in any way we know of.

It'd be more like saying Finnish or Hungarian are a variation of Latin or German. Some small amount of shared vocabulary (and maybe phonetics) due to proximity, but no more.

Irrespective of the relation between Japanese and Chinese, the immense contribution of Latin found within modern European languages is a given as anyone armed with a dictionary can deduce for themselves.