User blog comment:Ahomeschoolingroudon/Season 5 Early Hints/@comment-25656629-20151110133644/@comment-25968390-20151110221951

Well, obviously Carmine doesn't count as an answer technically, but maybe it could spark an Idea for an Under Night IN-BIRTH related fight for Season 6? Just a thought... Anyway, I have an emergency guess I'll reserve unless the next guess is wrong as well...

Ganta X Skarlet? Skarlet seems like a blood mass in the form of a ninja of MK fame.

I'm reducing my choices based on what's left on the Superpower Wiki (Can't fragging believe I'm still using that...), in comparison to your sources... Just So You Know...