If you're a newcomer to the series, then you'll likely be wondering where you should start. You're probably going to see a lot of different opinions on this topic, but for the sake of this article, we're going to try and look at the situation logically.
First off, if you want to explore the mainline games — that is, Yakuza 0 through 6 for Kiryu's story — then Yakuza 0 is a great place to start. Not only is it one of the best, most beloved titles in the franchise, it's also the first mainline game chronologically. It's a fantastic example of what Yakuza / Like a Dragon is all about.
Yakuza Kiwami isn't a bad option, either. It's a remake of the very first Yakuza game which originally released on the PS2. However, parts of it haven't aged especially well. The storytelling feels quite basic in comparison to the games that came after it, and the same is true of the gameplay structure.
If you don't want to dive right into the main series, then we'd strongly recommend checking out Judgment. As mentioned above, Judgment follows the same gameplay blueprint as the main Yakuza games, but it's a totally standalone story with its own cast of characters. Chances are, if you end up liking Judgment, you'll like the other games in RGG Studio's catalogue, making it an almost perfect place to begin.
Like a Dragon: Ishin! is a good shout as well, although its 1800s setting does make it feel like a very different experience at times. But if you're a fan of samurai movies, it's an easy recommendation — and it may just be an effective gateway to the broader series.