Kumo had to rest for a few hours after casting several high power spells, and at the end, he used a dimensional door to leave. The guards in question were not very competent, as you can see, and in panels 5+6 Kumo is invisibly there. He stabs them and throws them off. There's actually some of their blood over on the ground at the end there.
I hate the way his mustache came out but the more i messed with it the worse it got.