Nabiki having recently arrived first went to her room an un packed her things an took a shower then dressed in her school uniform from her old before going out a seeking her classmates.
It wasn't difficult due to the larger number milling about as if lost so before she makes her presence know she observes. 

It seems as if they are engaged in a mock war game that's goal is to capture one of two flags

"How Childish" she thinks 

There is no discipline among either team and as a result no thought out plan of attack or for that matter a defense.
So sitting down and gathering her knees up by wrapping her arms around her legs then resting her chin on her knees she takes the position of un involved observer.
Her choice of location give her a good view of most of the action while also limiting her chances of drawing attention and still appearing not to be hiding.