Finished with vol 6. Not much happened in this volume, the Silent Zephyr's attack only take a small part of the chapter, but what a cliffhanger. Clarifying what zephyr325 write about vol 6 before, here's how the battle goes.
Spoiler for vol 6 battle:
Chal and laura were hit by surprise attack so they retire early. Next, they tried to team up against M, but Ichika's power run out from defending M's attack, and Rin was hit protecting Ichika.
Ichika escape from battle momentarily to recharge his power using Houki's IS skill while Cecilia take Silent Zephyr alone, she was outskilled, but manage to shoot M using the new skill " The Flexible" before her IS fall.
M was about to shoot Cecilia, but at the last moment, just like a typical shounen hero, Ichika arrives in time to slash M's rifle and saves Cecilia(Cecilia could have died if she is shot since she purged part of her IS armor as a last resort so the shutdown system of IS won't work anymore). The Silent Zephyr actually can still fight on, but Squall order M to retreat for reason unknown(earlier, Squall also confront Tatenashi and run away even though she still have a pretty good chance to win against Tatenashi)
Will write more summary after I return from dinner with my family ^^