Hey there!
Currently working in Tokyo. Have lived in Japan about 9 years now, 7 of which have been working various places and companies.
From my personal experience, moving here was the best decision I've ever made. It put me on the path to becomming fluent in Japanese, got me a job in the video game industry and allowed me to meet my boyfriend who I now live with.
I've seen others who have had a terrible time here though. A lot of people complain about Japanese people being cold, stand offish, and shallow but the people saying that almost always have trouble speaking the native language. If you cant speak any Japanese, you might want to set your expectations so that you wont be dissapointed when you struggle to connect with the native population. That can also be a motivator to learn the language just be aware it will take time before you can speak at a level where you can have meaningful conversation. On the other hand you will be in Tokyo where there is a higher population of English speaking Japanese and other foreigners you can meet to continue having a healthy social life.
Just keep in mind life in "Tokyo" and life in "Japan" can be different in a nuanced way. Tokyo is a huge metropolis and has all the caveats that come with it the same as New York, London, etc. It's still uniquely Japanese but be prepared for the same crowded streets and rude people you would expect elsewhere.
Do you know what the working conditions will be like? Standard Japanese salaryman life can be quite taxing with the amount of overtime and often dumbfounding work culture. However, since you seem to be getting this job through your current company if the expectations and way of operating is the same as what you are used to then it shouldn't be a problem. Basically,its important to consider whether you will be working the "Japanese way" or the same as back home.
One thing stood out to me, and I dont mean to pry or be too personal, but you mentioned wanting to start a new life somewhere else. I've seen numerous people come here with the same intention only to realize changing where they lived didn't solve any of their problems, or that the problems they had here were even worse and eventually go back home. How well you enjoy your time here will depend on what your end goal is and what your expectations are. If you are in a stable place mentally and emotionally and are just looking for new experiences and not worried about being on your own, across the world from any support net work you may have and not afraid of the feeling of loneliness many experience in a big city where they dont know anyone I think you will be able to adapt and have a great time. If your desire to come here stems from dissatisfaction with your current situation and you hope Japan will be a solution to your problems, in the experience of what I've seen I think you will ultimately be dissapointed.
Having said all that I still love living here. I hope I didn't make it sound too gloomy or negative, just wanted to give some realistic insight. There are a lot of great things about living here, but having been here so long I have actually started to miss some of the good things about America and with aging parents on my mind I've actually started to look for employment back in the states again. I think with the right mindset you can have an amazing time here. If you have any more specific questions please let me know!
