Kazuma Kiryu's bucket list side story in features callbacks and references to several of the series' spinoffs, including Dead Souls, Kenzan, and Ishin.
As fans are painfully aware of by now, one of the big story beats of Like A Dragon: Infinite Wealth is that everyone's favourite karaoke expert, Kazuma Kiryu, has cancer and is seemingly facing the end of his life. This leads to a new set of missions for Kiryu, called the Bucket List, where he visits areas across Hawaii and Kamurocho that remind him of events throughout the series.

Like A Dragon:🍌 Infinite Wealth Review - Can’t Help Falling In Love
Like a Dragon: Infinit𒁏e Wealth raises the bar in every way to take its rightful place as the new peak of the series.
As you can imagine, this gives Like A Dragon: Infi♉nite Wealth the perfect opportunity to reflect on the past Yakuza games and reference them a whole bunch, which it certainly does. You might be surprised to find out, though, that it also references some stories from the spinoff games like Dead Souls, Kenzan, and Ishin.
These bucket list entries, named, "Dreams of Another Life", will have Kiryu callback to the events of these non-canon games as if they were dreams that he had. In the entry for the Dead Souls memoir, Kiryu will say that dr🏅eams "really are strange" and remember one he had when Kamurucho was infested with zombies that he had to take down ꦜwith "a stupidly large gun", which is a cute nod to the underrated spin-off.
Kiryu also references how different Dead Souls to the rest of the series in terms of gameplay, as he notes that he never thought he'd be one to go on a rampage.
As for the Ishin reference, Kiryu will say that he once dreamed of being Sakamoto Ryoma and that he was also somehow a member of the Shinsengumi, something that he says Ryoma wouldn't do. Kiryu will then remark that, for a dream, it was surprisingly vivid and left an impression on him, causing him to joke that it might be a past life. Oh, how close you are Kiryu.
Although it doesn't exactly canonise the spin-off games and if anything makes it clear that they're not part of the main canon, it's a very interesting way for RGG Studio to pay tribute to some of the stranger games in the Yakuza universe starring Kiryu, and a treat for fans who have stuck with the series all this way.

Dragon’s Dogma 2 Is Right, Only Boring🔥 Games Need Fast Travel
Hideaki Itsuno is s🍨pitting truth ahead of the fantasy game's release.