Once you find the three Medallions and place them in the statue in the Police Station’s Main Hall, you will descend into an underground tunnel.
The route is fairly linear, so you will not need many directions for now. You begin inside an office that serves as a safe room. You will find Flame Rounds, Gunpowder, and an elevator that will take you farther underground.
Continue descending to the bottom, ignoring one of the doors, to find a Hand Grenade beneath the stairs.
There is a display case beside you, but it is sealed. There is also a gate that you cannot open. Go up the stairs, pass through the open door, and cross the walkway. There is only one possible route, so keep going until a cutscene begins when you attempt to move a cabinet.
Your first encounter with G will be quite tense. You are trapped in a network of narrow corridors where the monster will chase you. First things first: its weak point is the giant eye on its shoulder, so try to shoot it. There are healing items and ammunition in the corners of the area.
Other than that, you should obviously try to keep it at a distance. It can charge at you from afar, strike you with the pipe in its right hand, or attempt to grab you. If you have any grenades, some of which can be found around the area, you can use one to escape when it grabs you.
You must be extremely careful when the area fills with steam and it disappears, as it will leap at you after a while and become more aggressive. However, it is already badly wounded by this point, and a few more hits will make it flee.
After the battle, you will see a ladder drop down. Search the entire area before climbing it, collecting anything you did not pick up during the fight against G. Then climb the ladder and turn right to enter a small office. You will find a Green Herb and some Gunpowder.
Follow the only available route and pull a lever to move the walkway so that you can continue.
In the safe room you reach, you will find a Hip Pouch inside a locker. Then climb the ladder. You will arrive at the Parking Garage. There are no items here, so approach the gate and examine the machine beside it.
After the cutscene, you will need to find the Parking Garage Key Card.
