If you want to study in Japan then some Universities require you to write an international student exam on topics like Maths, Physics, Biology etc. Also there are some courses entirely taught in English but science subjects like Computer Science are only taught in Japanese. The JLPT I think is needed for some Jobs and most companies will more likely choose you if you speak Japanese; however, both studying and working requires a VISA which I think lasts for 3 to 5 years. After 5 years or 10 years in the country I think you can apply for citizenship.

Getting back into learning something is hard but starting to learn a foreign language is also hard especially in the case of Japanese because it is hardly spoken or seen in South Africa.

I would recommend the book 'How To Become Fluent'. The book talks about how adults can learn a language better than children and even makes use of techniques of learning as well as cognitive science to show how it is possible for someone to acquire a new language at an adult age (21 for example).

http://www.takeal*t.com/becoming-fluent/PLID38809336 (replace * with o)

It costs about R400.

@Vice Cerberus: Just take the plunge and get back to it. If you want something then work hard for it. Tae five minutes a day to a learn a few words, while waiting for something you can revise grammar, make use of language sharing resources such as HelloTalk and HiNative etc

A quote from Michelangelo might just spur you on

"If people knew how hard I had to work to gain my mastery, it wouldn't seem wonderful at all."

Good luck