I just started Dungeon Crawler Carl. In it he fights a Spanish speaking boss. The Spanish is not translated (so far) and if you can read it, it really changes the mood and impact of the entire scene.
Are there any other books that hide significant plot points behind the use of foreign language?
Yeah if anything it’s a running theme of the series how the people who are caught in the collapse and the people who are made by the corporation are as abused as the crawlers