I know what you are thinking, yay another manga part! (all in sarcasm) Just hear me out.

Yami, did not wanted to see Yugi crying. He knew if that happened he might break down and make their efforts useless. That light smile was to hide the tears that were flowing in on the inside. He told Yugi to stop crying his tears for Yugi's sake. It hurt, it hurt a lot Yami wanted but would not cry. For he was crying for him.