I was wondering how Sengoku was going to be the foil to the MC and turns out he wants to make MC his attack dog. Sengoku's choice of targets will gradually be more and more insane until MC refuses, at which point Sengoku will use the incident in the intro as blackmail material. IMO eventually MC will be forced to do something irreversible to free himself from Sengoku's clutches and the author will try to ask us: what exactly is justice? Even if the story unfolds exactly like my prediction, I'd still be interested in how this author executes it.
This is an interesting way to look at vigilantism and I don't believe for a second that it's not realistic. Actually it is very realistic that there will always be some scumbag who wants to co-opt citizen movements.