Hey, new here and wanna add my 2 cents. I think part of the method of defeating Nurarihyon involves keeping him dismembered. Remember that Osakan Newbie who somehow managed to run off with Nurari's head for a while (pretty hilarious that he's still alive). Imagine if someone used the Y-gun to send off the head while it was still separated from the body.
Overall, I think this mission is going to demonstrate how getting 100 points doesn't automatically make you a pro at Gantz. Remember after the Oni Mission, several of the Tokyo team racked up over 100 points thanks to they're training sessions.
George, and Kuwabara both kept on using their H-guns on the Tengu and Kitsune aliens without killing them. I don't think they actually faced a target that ranked higher than 50 points before this mission. It seemed like they could have dispatched both aliens by using the H-guns to hold the beasts down and the X-gun to blow their heads off. I think the 100 point's weapon is only good against the high pointers when you know what you're doing.
For all we know most of the Osaka Team could have been extremely lucky. And Oka might just be an even sneakier Nishi who has survived long by choosing not to fight. If he doesn't think he can win, he'll back off and wait for someone else to kill it or lose his points. I think Nurari is as much a surprise for Osaka as it is for Tokyo.
Also, I wonder how many points the Kannon statue alien was worth in the Buddhist temple mission.