正義マン (せいぎまん, seigiman) is a relatively new slang term which literally means “justice man”. It is a pejorative term which sardonically refers to “do-gooders” who are always seeking for someone doing something immoral or unethical, no matter how trivial, and revile them ostentatiously to show off their moral superiority. Presumably, most of them also play a role as “自粛警察” (“self-restraint police”); you can refer to the lick at the bottom for its meaning.
Origin: Japan’s New Consumption Tax System
This word became popular when Japan’s new consumption tax systems were introduced in October 2019, which tax takeout meals at 8% and dining out at 10%. This rule applies to every store that serves food in Japan, including fast-food restaurants and even shops at food courts. This means that, if you buy food at a food court and bring them home, the tax rate is 8%, whereas if you intend to eat the purchased food sitting at a table nearby, you ought to pay the extra 2% upon your order for your “fine-dining” option. The more ambiguous and controversial case is when you buy food at a convenience store and eat them at its tiny “eat-in” space, which usually can accommodate only a couple of people and is located at the corner of the store (with or without chairs). As in the food court, you’re supposed to pay the 10% tax if you intend to “dine-in” at a convenience store, otherwise at 8%. — however, there might be a case when you buy food as takeout, but later “change your mind” and eat them at the eat-in space. Although some people, i.e., 正義マン (“justice man”) severely criticise this act as イートイン脱税 (“eat-in tax evasion”), the reality is that nobody has been charged with the “tax evasion”, making it a very controversial and ethical issue.
Right after the tax systems were introduced, the word 正義マン (“justice man”) started to be used to describe those who persistently snitch to staff at a convenience store on people who commit “eat-in tax evasion”. Although they believe that what they do is “a fight for justice”, many people dismiss them as pedantic and moralistic. However, people who deserve the most criticism are obviously those who have decided to introduce such complicated and ambiguous tax systems in Japan.