The Garlean wearing glasses who travels at Asahi's side is not on board with his antics and will team up with Alphinaud to help bring Asahi and Zenos to justice as their actions are detrimental to the well being of Garlemald itself.

Unlike the Elezen who accompanies Asahi, the Pureblood Garlean has a unique design which suggests he will play an important part in the story moving forward. He's also presented as being mild mannered whereas his Elezen companion refuses to speak to the Warrior of Light and is shown in the 4.3 trailer as gearing up for battle.

I think it's possible that not everyone in Garlemald knows of Zenos' return and that at the very least the rumours surrounding his defeat are muddied enough that the truth is difficult to ascertain.

It's possible that this figure could very well be our 'Larsa', or at least a step towards friendlier ties with the more moderate Garleans. Perhaps he's genuinely a part of the Populares faction whereas Asahi simply pretends to be?