Heading back to the Egg Corridor you'll quickly see that something terrible has gone here, as the entire place has gone to shit. Everything is cracked and broken, the entire place has collapsed into a new level, and dead dragon babies litter the ground…
Don't get too sad though, as soon you'll start running across undead baby dragons that will make you wish they all died. Also keep an eye on the ceiling, the further you go in, the more of those stalactites will fall down. The bigger ones prove fatal if they connect.
Once you see this thing, back up! It's a time bomb and has an insane radios. After it explodes, continue deeper.
Enter this building by a broken open vent, and leave by the other vent in the bottom right corner. Feel free to grab the chest, but if you do, you'll have to defeat an optional boss fight.
Check up on Egg no.0 at the end to be offered an escape with Kazuma in the Dragon whom successfully hatched from it. This will trigger the Bad End and you'll miss out on the rest of the game, but if you saved just before, feel free to experience it and just reload the save after.
Follow him outside to the outer wall of the Island, and use whichever Booster you have to scale the wall.
Up the top of the wall you can enter a door into a Storehouse where a transformed human gets scared of you.
Save up, and head into the other door to find the Plantation.