For what it's worth, you can save often outside of big story events, and in most cases there's a big spot on the map so you can see where that will trigger. It might take a long time collectively, but the only long play sessions (depending on what you consider long) would be the big event progression.
As for me, I saw the original trailer and a guy hit another guy with a bicycle and I was sold. Got it that a few days after it came out in 2006 and played through it, that US dub was not what I would call the best. Missed a couple of coin lockers (I only know this bc I recently found a printed out list of them, which I had marked off as I went, and somehow still messed it up), but otherwise thought it was fun.
I own physical copies of 2, 3, 4, and Dead Souls, but have never played them. I have 0-6 and the first Like a Dragon on Steam, but I've only ever poked around for awhile at Zero, and it's really good. You can just go beat guys up, or challenge a girl's score in the arcade, or go knock the shit out of some little kids at this toy car racetrack. There's a lot of stuff to do. I don't know if it continues in the later games, but every time I find a girl's card in Zero, I google her name with "jav" to see the titles of the pornos she was in. It's never normal shit. It's always like, "my lactating tits shot all over the principal's wife's ass? omg" or something. So funny.
I intend to sit down and play through them all at some point, but I get too sidetracked by deep dives into other stuff. In Zero, I was up to the point where the focus shifts and there's a minigame that I think you only need to do once, but it's better if you do it a lot, and then something else came out and I forgot about Yakuza. But one day, I'm gonna do it all. Mahjong and all that.