I love that you wrote a ninja story… I JUST wrote a pirate one… Ninja vs. Pirate: GO!
I think their laughter part is a little confusing. You can progress quickly through action following the standard formatting easier because people are prepared for it. If you do something new it draws attention to it and slows down reading.
How does this sound:
The six guards lined up and laughed at the peasant, “Haha-” Their laughter stopped as is began.
It could be the line break that made me pause though. But awesome story, keep going!