Not knowing where to go, the girls all meet in the main lobby; Rika seemed to predict that, and was waiting in there.

Rika Hoshikawa
"Oh, there you are! Sorry for the inconvenience, but it seems that beast you fought earlier was part of a larger incursion! Quick, come in here!" She guides them to the hall next to to the lobby where, behind an old painting which slid off, a hidden elevator that leads down.
When everyone is inside, Rika press the buttons, and the metal ornate grid closes, the elevator quickly descends... And descends.
After seemingly some ten floors down, it finally stops: the girls can see a huge complex, with them landing on a platform where multiple people in uniforms worked on tables full of different displays and buttons, at a central table, Moriyama stood, waiting for them, next to Hoshikawa, both wearing military uniforms, displaying their high-patents and multiple condecorations from the War.

Shinzo Moriyama
When everyone is by the table, he starts:
"Listen up everyone: We spotted multiple shamons on the Reiganbashi docks. Our intelligence believes they came together with that beast you fought earlier, but kept hidden...
The area has already been evacuated by Mimoza Division, we just now need to eliminate those shamons before they destroy the whole area, or move to threat a non-evacuated one.
this is going to be your first deployment as the Acrux Division of the Steel Petal Force... Please, do your best!"
And with that and a salute, he dispensed you to go into the petalframes... Those jewels of steam-technology, currently the greatest weapon of mankind against the shamon threat, powered by the warrior's own soul (and currently an auxiliary battery... They're working on that)!

Rika Hoshikawa
"Heh, I'm still working on your uniforms, so today you will have to fight in your normal clothes~" She said, smiling embarrassedly and showing her tongue,
"I-I promise the wait will be worthwhile! For now... Though it isn't ideal, there's no big deal about not having them either... You will just have to put this on..." She says, showing them greyish-brown capes, that would their shoulders and upper body like ponchos, it seems made of some rubbery polymer, and has plug-holes in it,
"This capture your spiritual power and make sure it goes into powering the petalframe, instead of dissipating in the air!"
When it's all set, the girls are inside their open petalframes, wearing the cape, with cables connecting it to the petalframe's interior. As they're unplugged from the cables powering the auxiliary battery and turn initial ignition, they start humming, louder and louder, until steam jets blow from exhaust pipes in their back.
Rika gives them each a big key-thing, around 40 centimeters long, though not very heavy,
"These are your soulkeys, each are attuned to the owner, and are used to start your petalframes!"
After starting them and getting in position, the girls can move them freely, like the thing is just an extension of their body. After some initial trying, they can also conclude they're pretty agile, in fact, with steam propulsion, they can slide and dash at great speeds.

Akira Hoshikawa
"Alright, now to you getting there: the petalframes are capable of locking on the railways and using their auxiliary power to drive at full speed stably on them. Gagrux and Mimoza divisions will work to set the best pathway, and to redirect any obstacle... Now, good luck to you!"
On the meanwhile, on the island district of Eiganbashi, encircled by the canals and the Edogawa river at south, where some habitations lie on the northern side, while the southern is occupied by dockyards.
The place was completely desert and quiet, one could say, until the silence would be invariably interrupted by a roar and destruction. There are a bunch on shamons in there, smashing buildings and infrastructure.
[ +- ] Illustration of the shamons