This is something I've always wanted to see done in anime form ever since I played Deus Ex but I know it's probably a pipe dream. I gotta get it off my chest, though.
>Protagonist is a salaryman, describes how he spent his whole youth indoors studying at the behest of his mother, he did alright in school despite that, but still lost out on his childhood
>Wakes up at 8 AM, goes to work before his boss shows up, stays only until after his boss leaves
>Returns home (when he isn't obligated to go to company bar outings) to his 300 square foot studio apartment
>Has fallen into an ennui, life goes on
<Until one day
>Is witness to a crime where a beautiful young girl gets raped, he is just out of sight from the perps but he doesn't do anything out of shock
>Perps number about 5, one on lookout, they look professional almost
>Girl is abandoned for dead after the rape, protagonist only then tries to save her but he's too late so he calls an ambulance at the location and legs it before he gets blamed
>Watches the news day in and day out trying to find out what happened to the girl, if she got revived by the ambulance, etc
>Finds her story come on air, they say she merely died to an accident after prostituting herself then leave it there with no follow-up
>Protag becomes immensely pissed, takes matters into his own hands, partly out of duty and guilt since he let it happen and could have saved her if she was quicker
>He goes back to the location of the crime hoping to catch any of the guys who he saw that day (he can't forget the scene no matter how much he tries so he recalls their faces with perfect clarity)
>Sees one of the guys happen to snoop by, he follows him to where he's going, he leads the protag to an alleyway in the middle of some seemingly-empty buildings
>The guy he's tracking noticed at some point he was being followed, decks the protag and starts beating him up
>Protag desperately fights back and gets lucky, swings a pipe he finds on the ground and knocks the guy out
>Protag stands over the knocked out perp, is contemplating with himself for what felt like hours
>He crosses the Rhine and decides to kill the perp, smashing his face in with the pipe
>Before he makes a run for it, he searches the perp's pockets and gets his phone and some other notes, implies it has info on the other people he's working with
<Including a picture of the girl he raped that day
>Protag returns home, evades getting caught for now, and plans out his long revenge
To sum up the rest of the story...
>Protag gets caught up in a huge conspiracy, the Yakuza who raped the girl are actually working for the government for their mutual benefit
>Protag, now fully devoted to his new path in life, moonlights as a Punisher-esque vigilante, bringing justice to the yakuza and the government officials working with them
>He uncovers more lies and dirty secrets along the way
>Series culminates in him taking out a big-name Yakuza (not the head honcho, mind you) who was responsible for numerous crimes all hidden by corrupt gov't officials
>Protag lays low, covers his tracks afterwards
>One day wakes up tied to a chair in a dank room, the big-name Yakuza guy's buddies and HIS bosses surround him
>What follows is assumed torture and death for the vigilante
<Cut to a few weeks later
>The protag's home is searched after his body was found, one policeman (a side character for the whole series who was there to show the perspective from the police force investigating the protag's murder/justice spree) uncovers a journal and full dossier the protagonist wrote to keep tabs on the whole operation, starting from the rape incident to his final big kill
>The policeman pockets the files without his superiors knowing, sets up a sequel where the policeman takes over the role
<Also been playing with the idea for an ambiguous ending where the viewer has the responsibility to take on the role of the vigilante themselves, since the idea is that "nobody will do your work for you" or something like that
As you can tell, the idea rocks the boat a bit too much to ever be accepted in the highly corrupt society that is Japan. A man can dream, though.