"Hugs, holding hands, patting heads... all of that can help. Even more if someone is feeling very, very sad." He had noticed that the color of her collar became lighter, slowly, but certainly, so he tried to distract her from her shadows if he could. He wouldn't point it out to her that the fluid in her collar was changing. He wouldn't even want to know what his own looked like at the moment.

"Giving small gifts to show that you are thankful for what a person does can help as well. Yotsuba might be small, but she can do more than she thinks."

Because she is human. And humans always did things that amazed him even if they were simple.