Yorimitsu-sama

https://www.reddit.com/r/hanakokun/comments/tidz2x/yorimitsu_supremacy_just_look_at_him/

This is a photo with a theory commented by r/hwaetnow. What we 'know' is that he is an ancestor of the Minnamoto family. Not much else, other than the fact that mystery no.6, Death, has a flashback involving him.