Diarmuid gives him a gentle look and then ruffles his hair, "What about this? Often it seems like we dream about whatever we are thinking about when we go to sleep. Think of me telling you silly stories about my past or singing you songs. That would likely bring on better dreams than thinking about how sad you are Ayaka was taken again, right?"

Eventually his brother will have to probably dream about those sadder things especially since their dreams seem to be less dreams and more processing memories of things that have happened to them, but it doesn't have to be now. Not when there are other things he can try to focus on.