I did not realize that Road to Perdition was based on Lone Wolf and Cub. But of course it is. D'oh! on me. I guess I need to reread Road to Perdition now, and think about how it took the main story arc of a 28-book series and condensed that down to one novel.

I was thinking about Daigoro, the "cub" who's been raised as a stoical assassin and who has seen every kind of bloodshed, murder, violence, and sex that human beings can perform, even though he's just four years old at the end of the series. Not to mention his father constantly leaves him behind and sometimes leaves him to die. What a messed-up adult Daigoro would grow into.