The third volume is yet another great addition to the series, and some really important things happen (more on that below). This really is a great series, and if you haven't seen it yet, I reccomend you go get volume one (get the series box. it's worth it) ASAP.
Anyway, in this volume some interesting things happen (Spoilers ahead, don't read 'em if you don't want to know. You've been warned.)
Mimori was thrown in a jail cell after talking to Zigmarl about what exactly HOLY's doing. Thinking she'll never excape, she starts writing down thre truth on a little pocket computer thing, but Eelian (who was watching her) destroys it. However, Cougar comes and breaks down the walls in some dramatic Cougar-style rescue, gets her and her stuff, and brings her to the airport with a ticket to escape to the mainland. However, she chooses not to go, and starts wandering around Inner until she meets up with Asuka.
After his last fight with Emergy Maxfell, Kazuma was unconscious for two days. He wakes up mad - really mad and heads to meet Kanami so he can eat and then go find some more HOLY members to beat up. However, he and Kimishima discover that the farm Kanami works at was destroyed by HOLY. Kazuma starts fighting with the guilty members, the Darth Dozens (or Dars). Kimishima goes out and finds Kanami, until the two are captured by HOLD and taken to the same place where the rest of the farm workers are being held.
The news stations find out about the fight and get footage, which is broadcast on TV and seen by Mimori, Asuka, all of HOLY and HOLD, Kimishima... and Kanami. Kanami finally finds out that Kazuma is an Alter User and why he's always been running off, and she and Kimishima escape from HOLD to go find Kazuma. Kimishima drops Kanami off on the way, to keep her away from the fight, and finds Kazuma. He helps him win, but falls unconscious. Kazuma carries him back to Kanami, but he dies on the way. This Kazuma gets really mad and starts attacking HOLD units. Ryuhou goes after him, but finds Kanami, and Kazuma catches Scheris. Each angered by the actions of the other, they find each other and start fighting. Neither one really wins, because Kazuma's second-level Shell Bullet opens up a gate to the Other Side - a land of psychadelic Altery-ness that generally gives you a headache if you watch it too long.
This causes another earthquake and land upheaval, throwing the Lost Ground back into chaos. Eight months later, both Kazuma and Ryuhou are missing. Kanami is captured and used as slave labor by an Alter User named Dread Red, until a mysterious stranger comes along and stars fighting with the overseers and Dread Red's Alter (which I think is called the Delay Octopus... in any case, it's a big, ugly squidlike thing). Our mysterious hero turns out to be none other than...Ryuhou... with total amnesia?
The volume stops there in a massive cliffhanger, so you'll have to go get volume four to find out what happens, but it really is an awesome addition to the series, so go check it out if you liked the first two volumes.