>>283171409
Retsu's an odd character in the cast in that despite his age he doesn't really grow technically or physically but only mentally.
Whereas Baki, Jack or Katsumi learn new techniques or come up with new stuff rather regularly throughout the manga, Retsu only really learns Xiaori from Kaku right before he's about to die, even during the boxing arc he doesn't really learn new stuff as much as he's getting used to fighting with a peg leg, on the other hand he has a massive mental and emotional growth compared to most of the cast, which is odd because usually that's something Itagaki does for the old fellows like Doppo or Gouki.
When you look back at all the previous arcs it feels rather strange, Retsu feels surprisingly static as a fighter but as a character he's one of the most compelling when it comes to growth, it's probably why he's so beloved despite starting out as an absolute jackass and ending as one of the most affectionate and cherished bros.