Responses
I think it's the term "aniki" it technically means older brother but is used by yakuza for ppl who are above you in the hierarchy but aren't the boss. If I remember correctly, the guy who killed him in after he was reincarnated was the person he killed in modern era in the first chapter, a subordinate from his group that was acused of betrayal or something like that, he'd have called Ranmaru big brother due to yakuza customs

Who's Hajime again? I can't remember all names