Japanese is a unique language. Despite decades of research and investigation, Japanese has not been demonstrably proven beyond a doubt to be related to any other language on Earth, with the sole exception of the minority Ryukyuan languages spoken in Japan. Other than that, the language that comes closest to Japanese grammatically is probably Korean, which some linguists at one point believed might possibly be a distant relative of Japanese, as part of the Altaic Language Family Hypothesis, which has since been discredited. No genetic relationship between the two languages has ever been conclusively proven.
Kuwashii Japanese 