Kaiba doesn't acknowledge the extra support. Doing so and not immediately throwing it off would be admitting that he needed it. It's much easier to pretend he didn't notice.

"'f course," he said, straightening as much as he could. He's able to walk well, just more slowly and with shorter steps. If anyone actually saw them, he could say it was so that Atem was able to keep up. It still doesn't solve the most pressing problem of how to leave this island.

"What houses are on this island?" he asks suddenly. "I don't fell like dealing with a boat again."