A survival game a survival game

You go through the door and see stairs going downward. You wonder why that is and keep going down with your pet beside you.
You walk for only 5 minuted and see another door ahead of you. This should be underneath the forest, you guess. Without thinking, you go through the door and see...

A room full of machines operating and monitors indicating numbers.
The only two sentences you can read are

[System code 2404: Memory damaged]
[System mode 004: Jyukusui]

What does that mean?

continue