More evidence towards "Kiyama is Takiya" theory:
1) In ch133 Telne follows Takiya seemingly simply because she suspects him to be Elma's love interest, but when she confronts him it looks like there's something more to that. We don't see what they say, but Telne first points up (at her missing horn, that was cut off by Kiyama), then Takiya reacts with a surprise and starts apologizing.
2) At the end of the oneshot Kiyama says that if he ever makes a bond like their group had, he'll try to preserve it the same way the King kept their party together. And that's pretty much the role Takiya plays in the story. Like in ch33 he invites everyone to hot springs, and when asked by Fafnir what's his goal, his answer is "To make a comunity". Also in ch119 Elma characterizes him as "like the oil in the cog that makes relationships run smoothly".