Those whoever having income and saving in Japan, the investment is an unavoidable option considering almost zero interest rate of the bank savings. 

As an all-time busy freelancer, though, I do not have time on actively watching the stock markets or FX. Moreover, my purpose of the investment is to spend peaceful retirement life where I don't have to worry about the expenses when we cannot expect much from the government pension. 

Since 1st January 2018, the Japanese government has introduced a new tax exemption scheme for smaller investments (of up to 400,000 yen per year) for 20-long year, called Tsumitate NISA (つみたてNISA.) The scheme is to encourage younger people to build their assets by investments that can be deposited monthly as per choice. Before Tsumitate NISA, there has been NISA, where you do not need to pay the tax for the profit you have gained out of maximum 1.2 million yen yearly investment for five years (i.e., the total 6 million yen.) 

Here, you cannot run Tsumitate NISA and NISA at the same time (you can only switch between two each year as your choice.) Also, you can create just one Tsumitate NISA or NISA account at a time.

Therefore, I have been planning to open one NISA / Tsumitate NISA and another investment trust this year, apart from currently ongoing iDeCo and Kamakura Toushin investments. 

When I was keenly researching about NISA and Tsumitate NISA, I found helpful website introducing most of the beneficial scheme for the retirement planning. 

Retire Japan

What helps me the most is that the information on the website is in English so I can discuss it with Siddharth.