Trigger (TAKEMURA Yuuji)

Description From MangaHelpers:

In the near future, Japan has become a monarchy. The current king of Japan has created a shocking new system for decreasing crime. There is a person known as a "Trigger" in each prefecture and Tokyo. These people are allowed to shoot whoever they decide is 'evil,' whether its a violent criminal or someone who reads newspapers annoyingly on a crowded subway car. Mikami Kazuya is the Trigger of Tokyo. He wanders the city, leaving a trail of corpses of 'evildoers' in his wake. He also tries to use his homicide rights to protect his favorite restaurant, where the curry reminds him of a home-cooked meal. However, his efforts may do more harm than good to the poor restaurant. Will the Trigger system really result in a better Japan? [tethysdust]

https://www.mangaupdates.com/series.html?id=68974