This one differs from the previous keys the key itself is very well hidden, and there’s no way you’d spot it accidentally. This is the first the secret boss key actually opens a door – not a computer terminal or keypad.

Inside, you’ll find a big weapon crate and several backpacks, duffel bags and such. You’ll see a door with a “staff only” sign next to it. When you get there, go past the table with the laptop and turn right. Once you’ve beaten Kajika, you’ll have to find his hideout. Once you’ve grabbed the key, you’ll have to haul it all the way to the end of the mission.

Interact with it, and it’ll drop the key. Jump over the blue tool box and you’ll find a dead body hidden behind it. Turn left immediately and enter the machine room. When you get to the control room on the second floor, the one overlooking the courtyard with the twisty helix statue, go into the hallway leading to the stairs.