Please note: Full spoilers for Yakuza 0 and Yakuza Kiwami ahead.
The release of Yakuza 0 in 2015 added a new depth to the Yakuza series, particularly to its first entry. Coming a year before Yakuza 1 was remade as Yakuza Kiwami (and with both being released in Europe and North America in 2017), it gives protagonist Kazuma Kiryu an origin story. More than that, though, it gives depth to the antagonist of Kiwami, his oath brother Akira Nishikiyama.
Nishiki’s turn from devoted brother to power-hungry antagonist in Yakuza Kiwami has been discussed extensively, and nowhere better than in the YouTube video “Making a Villain.” The YouTuber Oni traces what 0 (and some additional cutscenes added to Kiwami) bring to Nishiki’s character. They demonstrate how the game shows Nishiki the mentor, the best friend, the vulnerable human being, and how these facets ultimately contribute to his downfall.