Under the circumstances, you decide that your best option right now is to stay quiet and keep moving. With evil ninja running around, the walls may very well have eyes and ears, so it's in your best interests to try and avoid doing anything that would draw attention. The idea of casting a spell of invisibility for superior stealth holds a considerable appeal, but you don't think it would be a very good idea to spring something like that on your allies without warning, and talking to them would kind of ruin the whole "stay quiet" part - not to mention that if you really are being spied on, some ninja mook might overhear your explanation of what your spell does, and tell his buddies to just blow up the hall or fill it with shuriken.
Yeah. It's not paranoia when the evil ninja really are out to get you.
So, you say nothing, and leave your magic alone. Instead, you focus on lightening your steps, controlling your breathing, avoiding contact with your companions, reining in your aura, and half a dozen other things that will, in their own small way, make you that much harder to detect. You give some consideration to trying to open up your various senses and watch for incoming threats, but only until the attempt to wake up your ki sense nearly causes you to lose control of your aura - which, with ki-sensitive ninja running loose, would give you away in an instant. It seems that you'll need a lot more focus and control before you can employ a ki or magical skill while keeping your energies undetected.
You can still keep your eyes and ears open, at least. Doing so lets you notice how Kasumi - and surprisingly, Yuki - are taking steps of their own to avoid making noise, pointers that you quickly appropriate and apply to your own rusty sneaking skills. You do have to make some adjustments, accounting for how women and girls walk differently than men and boys, but the corrections come almost instinctively. As for the other adults, they're not making any noise at all, and their body language and clothes - or simple distance, in the case of the two masters ranging ahead of your party - completely hide exactly how they're doing it.
Gained Concentration F+
Gained Ki Concealment F+
Gained Listening E
Gained Looking D
Gained Mana Concealment F+
Gained Spiritual Concealment F
Gained Stealth F+++
As for Altria, the way she carries herself as she walks tells you at a glance that she's making no real effort at stealth, aside from keeping her shield from banging on the wall or other acts that would immediately give away the group's position. On the other hand, the blonde isn't making much more noise than Kasumi. It would seem that being tiny is good for something after all.
Your decision to be sneaky turns out to be a wise one. About two minutes away from the box, Jo pauses near a corner, hugs the wall, and makes several silent, rapid hand-signs to Shiden, who conveys a different set of gestures back to Kasumi and Ayane. When both of them stop moving, the rest of you do your best to follow suit without crashing into them - Yuki has the least success, but Ayame manages to catch and support her. Shiden, meanwhile, has padded up to join Jo, and after a moment, the two men disappear around the corner.
There is a yell, swiftly cut off, and the sounds of a brief, intense struggle. Then Shiden returns to view, making a new set of signals.
"Two of the ones in brown," Kasumi breathes, her voice slightly above a whisper but not carrying as far. "Not any of the three that ran from the box, or the two that were left knocked out."
Gained Sign Language F+
You suddenly hear the familiar impact of fist against flesh - coming from behind you. Spinning about, you find Lu-sensei just putting the finishing touches on another of the brown-clad bad guys, while a fourth shinobi is slowly sinking to his knees, strangely-uncoordinated hands grasping ineffectually at the base of his throat and the feathery dart lodged there. After a moment of fumbling and increasingly unsteady breathing, the man slumps over sideways, banging his head against the wall before joining his buddies on the floor. Lu-sensei regards the man for a moment, then reaches down and frees the dart, which he hands back to Ayame. She accepts it with a smile and a gracious nod.
"Still a big softie, huh, Sis?" Yuki asks, eyeing the fallen ninja, who you can see is still breathing.
"Up to a point, Yuki. I don't see much reason for punishing the rank-and-file just because their superiors are aggressive idiots."
"Everything alright back here?" Shiden asks, approaching.
"We're fine, dear. Shall we move on?"
"As to that..." Shiden glances at you and Lu-sensei. "There's an emergency exit at the end of the left-hand corridor. Jo is checking it to be sure, but we didn't sense any guards, so it's likely we'll be able to get out. On the other hand - Master Lu, I take it you will be going in search of your other student?"
"You would be correct, Master Shiden." And then the old man looks at you. You get the feeling that he is inclined to send you along with the ninja, while he tracks down Cordelia.