Just a note, the collection title is a little misleading now that more games in the series have come out.
This includes Zero (prequel to the original series), Kiwami 1 and 2 (remakes of the first two), 3-5 remastered, and 6 (the original ending of the original series starring Kiryu). Seven meaty brawler games with absolutely cracked side content. Great stuff, good value.
That said, it does not include the new releases from Like a Dragon onward: Like a Dragon (turn based with a new protag), The Man who Erased his Name (side game with the brawler style of the originals, about original protag Kiryu coming back from "retirement"), or Inifinite Wealth (latest game in the turn based style, with a storyline crossover between the new protag and Kiryu, the old protag).
It also does not include the two "Judgement" spinoff games, brawler style games where you play as a detective in the same universe (these never got non-console releases).
Or any of the other even more obscure spinoff brawler games (most never saw release outside of Japan). Multiple "Yakuza but set in ancient history" games (one got a remaster released in the US), one "What if Fist of the North Star got a Yakuza brawler game" that is PS4 only (with a US release, hooray), and two PSP only games from Japan starring a side character in between the first six games (I think there are fan translations for these).
Just figured that might trip up anyone new to this great series that has a hell of a lot more games to it than most realize.