A conversation with @shiranuigenma got me thinking: what if Yamato has a severe pollen allergy? Kakashi brings Yamato flowers after the war and he’s released from infinite tsukuyomi because apparently people do that to cheer others up, and can’t believe the way Yamato reacts. Yamato would insist he’s fine and refuse to get rid of the flowers, but oh boy does he suffer.
Of course, Kakashi can’t help being amused by the irony of a wood release user having hayfever, although he does go to Sakura to get medicine when it becomes clear that Yamato is keeping the flowers, and will fish them out of the bin Kakashi has tried to throw them into if necessary.
The next time he gives Yamato flowers, he hands over some pills at the same time too.