I think the appeal of Kiryu is that, despite being a buff, hypermasculine tough guy we see him take time out of his day to partake in little activities that he enjoys. Yeah he's an unstoppable Yakuza badass, but he also loves racing tiny cars with local kids and that's great.

He can beat way through hundreds of goons, take down criminal conspiracies, and grab a combo from meal Smile Burger when he'd done. He loves unwinding at the arcade, singing Karaoke like a goofball, and spending time at the cat cafe! There's just not a lot of characters like that

Little things can very easily humanize otherwise hard-to-relate-to characters. Agent 47 plays the drums, Arthur Morgan loves history and drawing, Goro Majima is a big fan of baseball. Little touches folks!!!

Oh!!! And how could I forget: Miles Edgeworth secretly loves Steel Samurai!!!