Dead or Alive 6 is releasing them individually as well from what I've heard, just like DoA 5 did.
Edit: Yep, they are indeed:
$4 per character
MS also accidentally posted the core fighter versions of the fighters before they were supposed to, Koei Tecmo didn't want people to know there was a F2P version of the game releasing soon because they didn't want their sales affected, lol.
Nyotengu was a free preorder bonus, not dlc. But if the king of fighters season pass characters are only $4 each I will probably get them.