At a school
Japan.
within one year.
In descending order of ease: (1) Be born to Japanese parents and be brought up in Japan. (2) Be born to non-Japanese parents and be brought up in Japan. (3) Go to school in Japan. (4) Work in Japan. (5) Have monolingual Japanese friends. ...and so on. Besides the first two options, there are no easy ways to learn Japanese.
The ancient Japanese practice of Shinto is an interesting topic to learn about. Wikipedia is a good starting point, but the site Japan History is a better place to learn about it.
There are many schools that are specific to Japanese language, for instance if you wish to study at Japan, you are required to learn Japanese first, because the courses in Japan are in Japanese. if you fulfil the requirements you can go to Japanese language schools.
There are many different websites that are dedicated to learning Japanese. One can find a guide on how to learn Japanese on the Guide to Japanese site as well as the Guide to Learn Japanese website.
because the japanese want to learn and practice the interesting religion
For a serious answer you can learn about the Japanese culture and it does interest a lot of people because you learn about peoples way of life.
They learn the same things as we do in England but the learn more Japanese then English and they start learning engish in year 2.
Prince Shotoku inspired Japan to learn from China and helped spread Buddhism to Japan.
You obviously can't learn Japanese in one night. You could learn some key phrases that would be useful very quickly.
Japanese Characters, The English Language, (grammar, mathematics, etc)