I'm thinking of starting index investment with the new NISA for the purpose of asset formation in old age. Currently, I'm 33 years old and plan to deposit 50,000 yen a month at a time. I was thinking of investing in the S&P 500 or US stocks (VTI), but I was at a loss when I saw on Buffett Taro's YouTube video that there is a high possibility that US stocks will be sluggish for the next 20 to 30 years. Thank you so much for your advice.