Amateur Vigilante is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Action thriller about an obsessed lonely man with a delusional plot to save Japan by assassinating a politician. But his twisted plan is disturbed when he witnesses a young girl next door getting abducted by the Yakuza. He decides to save her but his attempt ends in a chaotic massacre where he manages to kill the gangsters. But things only get worse from here on out, now he's getting hunted down by even more ruthless killers.