Becoming a host for a parasitic dragon wasn't part of the plan. Actually, there wasn’t really any plan to begin with, but when the dragon egg hatches, Ashe figures it's time to come up with one.
Katsu's plans are failing miserably. His vast medical knowledge isn't helping Ashe's dragon situation, he's having problems staying detached, and the other mercenaries are concerned about their lifeforce being sucked dry and want Ashe to leave. Katsu is determined that if Ashe leaves, so will he. First, though, he has to make sure that his people aren't killed in battle... something they seem determined to do.