Togashi Yokuni is without doubt the most reclusive of the Champions. He is very much a hands-off ruler, letting what little interaction the Dragon clan has with the rest of the Empire be conducted by the Mirumoto family. It is said that the Dragon have a working relationship with the Scorpion, but as that information comes from the Scorpion most have some doubts as to its veracity.
The PCs recently performed a service for Yokuni, travelling to Crab lands to suss out a threat to the stability of the Wall. They found and defeated Hiruma Makasu, and held off a major Shadowlands assault on Shiro Kuni. They have not had any further contact with Yokuni, and most likely never will.
Togashi Yokuni is not available as an ally.