Leech Hunter is an unlockable minigame in Resident Evil Zero. To unlock it, simply complete the main game regardless of difficulty.
The minigame is accessed by selecting "Extra" or "Extra Game" on the Load Game menu.
On Gamecube and Wii versions of the game, players have the option to select Rebecca's and Billy's outfits with the "COSTUME CHANGE" option. Rebecca's outfits are "NORMAL", "LEATHER", and "COWGIRL". Billy's outfits are "NORMAL" and "JACKET". This option is omitted in the HD Remaster.
The "HOW TO PLAY" menu option brings up the following explanation of the game;
Find all the "Blue Leech Charms" and "Green Leech Charms" in the Umbrella Facility and exit via the Mansion's front door!
Leech Charms Features:
1. Colors and Characters
Billy and Rebecca can only carry a certain color of "Leech Charm".
"Blue Leech Charms" =Billy only "Green Leech Charms" =Rebecca only (Cannot be exchanged)
2. You Cannot Leave Items
Once the player acquires a "Leech Charm", it cannot be left.
3. Number Storable in One Block
Ten "Leech Charms" can be stocked in one item block.)
4. Number of "Leech Charms"
Blue Leech Charms --50 Green Leech Charms -- 50
"They're definitely there, somewhere!"
5. Game Over
If you exit through the Mansion's front door, or if Billy or Rebecca are killed, then the game is over.
A dead character's objects are not counted, so be sure to stay alive to the end.
We wish you the best of luck.
"You must survive in order to expose this nightmare..."
— Message displayed when game beings
Billy and Rebecca will begin the game with their respective Handguns, 200 Handgun Ammo each, and a First-Aid Spray each. Other weapons and health items are scattered about the map. There are three different possible gameplay patterns for the mode. Each pattern is chosen at random and affects item, leech, and enemy placement. The minigame takes place in the Umbrella Research Center and its basement. The majority of rooms are unlocked; however, some rooms are inaccessible, some are locked from the other side, and there are two doors that need to be unlocked using the Fire Key.
The health and behavior of most of the enemies is adjusted for the game. Zombies have much more health taking up to ten handgun bullets to drop, and tougher enemies have slightly less health, usually dying from a single grenade launcher shot plus a single handgun bullet. When the player's total leech count nears 100, some rooms become flooded with enemies, even those rooms that have already been cleared out.
After exiting the mansion or having a character die, the game will end and the results screen will be displayed. The number of leeches each character collected, the combined total, and average time taken to pick up the leeches will be shown. Last, the player will receive a rank based on the number of leeches they found and a prizes for the main game based on the their rank.
"You got the A Rank item, Infinite Ammo.
Any weapon you received during the game will have unlimited ammo."