How to change the language of Google Chrome? I traveled to Japan and bought a phone there. I changed the system language but websites keep showing in Japanese in Google Chrome, twitter.com for example.

Firefox is fine though so it seems like the issue is solely with Chrome. I tried completely removing and reinstalling Chrome but that did not fix the issue.
Usually websites that you visit will be in the language that they were made in.

My guess is that Google results in your browser are showing in Japanese and you're looking to change that. 

To do so, go to Google.com then scroll down to the bottom of the page. There, press on "settings" -> "search settings" -> "language in Google products" -> English (or any desired language)

Also change "region for search results, to "current region" as shown in the screenshots below.