Diarmuid might be little, but he knows far more than a little boy should about being strong. He gives Shinju a quick hug and then pulls his friend toward the apartments, "Lets go and get you dried off. I will make you something warm to drink and you can be just as sad as you want to be. Me, Lir, and the puppies won't tell anyone. We promise!"

In other words, it's okay to not be strong around him. He isn't going to think less of Shinju for letting his feelings out.