I want the older servant to tell us what happened to Seungho in the past. He probably knows him since he was a child and he seems to be the only one who cares about Seungho and is loyal to him.
Yashiro: I remembered just now. Before today, I completely forgot you all this time. But seeing that annoying face of yours made me remember. I'm no longer a kashira, by the way. Me: Yep that's them all right, fighting each other to the bitter end instead of making up.
Doumeki probably was expecting to run into Yashiro sooner or later. But Yashiro thought he would never see Doumeki again. That's why he reacted that way, he was caught off guard. But I think Doumeki knows Yashiro is trying to play it cool, he knows him too well.
Seungho is like... You can have him... No, actually you can't