Get on the right airplane.

I assume you must first, be an English teacher from a native English Country. If you are, then apply on Dave's ESL Cafe and other teaching jobs online sources and you will be short listed by the Japanese employers. It's by far worthier to go Japan than stay in China, if you can. I would, but I am no native English at all. All the best to you. 

I am also considering moving from teaching in China to Japan. There seem to be a lot of ESL teaching jobs in Japan if you look at Dave's ESL or ESL101. Most of these don't pay very well but it might be worth it for the much higher quality of life in Japan. 

Apply for a job through the internet, get ready to have a serious interview (on Skype) with a real (qualified) HR who probably speaks fluent English, when applying for the visa expect to have to answer a lot of questions and provide many documents about yourself because unlike China in Japan they are very serious about who can and who can't enter their territory.

The schools I worked for in Japan expected me to teach (German in my case) and not to be a white dancing monkey, when it was time to renew the contract I was evaluated on the progresses made by my students, not everybody is passed by the management in Japan so the students work hard and you can have a real classroom environment very easily, you don't have to spend more time on discipline than actual teaching.

Your employer probably won't try to scam you, Japanese behave like civilized adults and not like 12 years old bullies.

When it comes to daily life in Japan you will enjoy some of the world's best standards for services even in regular shops and restaurants, people are really dedicated to their work and truly enjoy doing their best for the customers. Japanese food is great, varied (much more than the stereotypical rice, fish and soy sauce to try), very healthy and cheap (cheaper than German food in Germany for sure), and you don't need to worry about what you are eating unlike in China, my favorite dish is okonomiyaki some sort of Japanese mix between a pizza and a omelet. If you don't like local food you can find food from any country in Tokyo or Osaka, whether in restaurants or supermarkets (Japan imports more than 80% of its food), slightly less choice in other major cities, Tokyo is the absolute food paradise, it has more recommended/starred restaurants than any other city in the world in the Michelin guide. The public transportation is so well developed and so cheap that cars are basically useless in major cities. The expat community in Tokyo has many different types of people (entrepreneurs, high-ranking managers, teachers, artists, ...) but overall is much more recommendable and has much less creeps and weirdos than in Shanghai/Beijing/Guangzhou/Shenzhen.

Japan is everything that China wants to but will never be 

Thank you for your answers. Regarding visa paperwork, would I need to return to my homeland (USA)? Though I am wealthy by Chinese standards, round-trip tickets to America would be a heavy financial burden.

If you need to ask this question on this forum than I am afraid you aren't going to cut it