There is an internet flea market service in Japan called Mercari.
I sold my Pokemon, which I bought more than 10 years ago.
I was very happy because I was able to sell a set of two games for about 5,000 yen even though they are more than 10 years old.
I bought the North American version to study English. I think that is the reason why I was able to get a high price for them, since they are hard to find nowadays.
But it still took a lot of time and effort to sell it.
I don't buy many things these days, and I may not use this service in the future. I will carefully select my belongings and enjoy a simple life.