I only played the first Yakuza when it released on PS2, and I intended to start again with Kiwami and work my way through all the episodes, but as you can guess, a quick google search showed me the overwhelming opinion that Yakuza 0 should absolutely be played before Kiwami, which kinda blows my mind because I've always been a staunch advocate of release order >>>> chronological order, always. Like, I wouldn't advise anyone to play Kingdom Hearts Birth by Sleep first, or Dante's Awakening before DMC1, same goes for a lot of things, in games, movies and books. I can't think of any other example where the consensus is so clearly towards chronological over release order.
So, alright, I'm gonna trust everyone on that one, I guess I'll understand why it is so once I'll have played both 0 and Kiwami. And luckily, it's been so long since I've played the original Yakuza that I've forgotten a lot of things. I mostly remember the final battle. Not sure about the ending, but I can sort of guess how it ended.