Yousuke never liked lightning, a habit carried over from Jiraiya. He dodges the attack nimbly-- Naoto is still hit however.

Both of them hold back. When a shadow looked odd like this one did, there was often some sort of gimmick attached to them, whether that was a specific weakness or an odd method of attack. they didn't want to trigger something nasty right off the bat and put them all in more danger than necessary.