If it's even possible to learn a language, especially languages like Japanese, in 6 months, you would have be buried in textbooks every singe day. Being fluent and knowing enough to get by in Japan are two very different things. There are people who go there knowing zero Japanese. Japan has become very tourist friendly over the years. As long as you can read signs to find your way around and read directions, you should be okay. Probably minimal conversation skills for asking for directions and buying things at stores.