It'll be interesting to see how many returning characters we get, given the 1000-year time skip. I wasn't expecting Hidetsugu, but apparently he merged with a demon in one of the novels, so sure why not.
Yeah, he got mad that his patron, the All-Consuming Oni of Chaos, lost in a fight with O-Kagachi, so he went and beat him up and took over the role.
It's heavily suggested that the emperor of Kamigawa is
Michiko Konda, who also became divine in the original story, as one half of the Sisters of Flesh and Spirit maintaining the boundary between the spirit and mortal realms.
There's a gang calling itself the Hyozan Reckoners, which was the name of the group Hidetsugu and
Toshiro Umezawa were in, and the boss is an Umezawa, though it's unclear if he's using the legacy or if he's a blood descendant (possible if
Kiku, Night's Flower got pregnant with Toshiro's child before he was banished to Dominaria). In the gang is a shaman who gets possessed by Azamuki, Treachery Incarnate (
Cunning Bandit).
So, there've been a few returned characters already. The set's central conflict is modernity versus tradition, so there will be a lot of throwbacks.