I still wouldn't have through Asahi would have been the one behind the marrage. Neither Asahi or Yotsuyu look like they are over 30 and frankly I would guess mid 20s. We also see in the echo flashback that clearly the garlean soldier sees potential value in Yotsuyu. I could see Asahi's position secured through Yotsuyu's marrage but I would doubt Asahi would have been that old when it happened and probably pretty tied up in his Garlean training. From Yoshi P's interview it sounds like Asahi spends most of his time in Garlemald.

Either way, I guess we will see soon. It would be a shame if the next Garlean we met was yet another villain. I will say that it sounds like things will definitely be more complicated than just executing Yotsuyu. I doubt that happening would cause much dissention in the population unless there was some important detail we didn't know.