It's a series that has always intrigued me. Finally bought one last month during a playstation store sale, Yakuza 5. Haven't played it yet and not sure if I should play any of the previous ones first before diving into this one. ¯\_(ツ)_/¯
well if you can find 3 it definitely helps. Being the first in the series for me, it had a summary of 1 and 2 that you could watch from the main menu to get you up to par. 4 is immensely enjoyable, 3 isn't. I'd recommend playing 4 because it has returning playable characters like Akiyama Shun, who first appeared in 4 and you'll know his back story then. You could simply pick up 5, play it and still enjoy it as a game, but you'll be lost on a lot of the stuff they are talking about. While 3 isn't necessary, it's not that good overall as a game either. I initially bought 4 and played it a bit, stopped and bought 3, not necessarily because I was lost, but I enjoyed it a lot so I figured "I should pick up the earlier games" and realized, wow 3 isn't as good.
Of the End/Dead Souls has NOTHING to do with the canon and all the characters have VERY clunky controls (although you get used to it fast). I still enjoyed it because it's a zombie spin-off and you slowly see the city getting worse and worse with more places blocked off, get hostess' to help you amongst other partners, and traverse through the sewers to get to other areas due to barricades. TONS of enemies to kill if that's your type of thing too.
These games are overly violent, which usually isn't my thing, but it's so over the top (slamming a guys face into the pavement and scrapping it back and forth) and not visual in terms of the gore, I let it pass because some of the things they do are laughable.
On a side note, I've been to Tokyo multiple times and due to the game I know my way around the area in the game. I can find the Club SEGA and Don Quihote etc. just because they are in the game (actual stores) and the streets match up exactly. It's surreal to play the game and then visit the place the game is based off.