Tax refund on pension

I got my lump sum payment of Japanese pension back when I was back in my own country. Now I am in Japan working in different prefecture from the last time. I would like to file for the 1) 20% tax that was withdrawn from pension and 2) the income tax return. My questions are:

1. Is it possible to file for 20% refund by myself? If yes, what are the necessary documents I have to submit to the tax office? Is it possible to submit them at the tax office where I am living right now?

2. Same as above, is it possible for me to file for the income tax return because I am not sure if my last company did it for me or not. What are the necessary documents I have to submit to the tax office? Is it possible to submit them at the tax office where I am living right now?

Thank you for all the answers.