Yes I have beaten both Kenzan and Ishin.
Am I not seeing it or are you missing Yakuza 4?
Played Yakuza 3, wasnt feeling it. Bought Yakuza 4 on sale. Loved it. I dont know why that one clicked with me. Still playing 5, not feeling it as much as 4 but still a good game.
Yakuza 3 was probably my least favorite and if that was your first Yakuza game then that would've been the worst to get introduced to. Yakuza 4 is currently my favorite and seeing as you loved it too then there's definitely a good reason why Y4 was really good. Yakuza 5 isn't as good as 4 but better than 3 lol