I would like the whole website to be read in Japanese and English. The body test for my "about" page and "product description" section on the product page is written in Japanese as it is a Japanese website first. However, when selecting the English language of the website, I would like for these specific section to be in English. These are parts that I had personally put into the website. If possible, I would rather be able to write this section in English as well as having it in Japanese as a base. Can this be done?
Having a store in multiple languages can be challenging. There might be "i18n" (internationalization) solutions that you could look at in the shopify app section.
Build a custom shopify store will give better result, and more flexibility. I would highly recommend it if you're working on a bigger project.