Japan's public broadcaster NHK is in a bit of 'toraburu.' While that word (hint: it means trouble) and many other foreign-derived words have wormed their way into popular Japanese lexicon in recent years, one combative protector of the language has had enough.

Local media reported this week that 71-year-old Houji Takahashi was suing NHK in Nagoya district court for ¥1.4 million ($14,000) for "unnecessary emotional distress" for the use of foreign words. Specifically, Mr. Takahashi cited words such as 'kea' (care),...