The YouTube mobile app has a feature that tries to auto-translate comments from languages you don’t speak into a language you do understand.
However, sometimes it acts weird. For example, in this particular case, as you may see, the YouTube interface language is English, the comment is in Japanese, and the translation offered is to Russian—of all languages! You would actually want this to be translated to English.
To correct that, you need to go to the language settings of your Google account—the same account that you are logged into on YouTube. Here’s what you should do:
Make sure that the option to automatically add languages is off.
Ensure that the preferred language is English.
In the “Other languages” list, delete the language that you don’t want the comments to be translated to—in this case, Russian.
This is what most guides will tell you to do when you search for this issue online. However, what they fail to mention is a very important detail: this option may take some time to apply. In this case, the change took effect a day later.
So, if you deleted the unwanted language but it is still visible as “Translate to” in YouTube comments on the mobile app, wait a day or two until the setting is finally propagated.