[The blue hair wrap is immediately recognizable even out of the corner of his eye, and from the way Hiro's reacting Minato can see that he and Korra must have been pretty close.

He says nothing at first, having been distracted by an odd sight- was it just him, or was Hiro putting more pressure on one of his ankles than usual?]

Let us know if he tells you anything useful. Whatever is happening at this altar can't be good, and we need to know the truth about it.