Moon - Walkthrough - Episode 4 - Chapter: Product Storage Sector I - Part 3
Major Kane fights the first mini-boss of the game: the Arachnid. He is very simple to kill. The Arachnid will start to shoot at you quickly, just evade his attack and shoot at him with your Muon Pistol. Stay far from the mini boss because he is able to stand up and falls and that will make a little shockwave that will hit you if you are too much near. Some Circular UFOs will help the mini boss to kill you. Don't care with them, just evade the fireballs and kill the mini boss. After this battle, Major Kane will find the Muon Pistol Ammo Clip increase and the Red Key. Captain Tsukigami will contact him and tells Major Kane that the marker that was on his location has just moved to several kilometers from there to the west. Now Major Kane has to go there.

ITEMS FOUND:
Muon Pistol Ammo Clip Increase
The Muon Pistol's clip size increased

Red Key
A Key to a lower stratum

Enemies:
The Arachnid Miniboss
Circular UFOs (less info)