This is absolutely unsettling. I was on edge the entire time, especially when Our Little Friend flew up to meet me at the top of the stairs.
I got some big SCP vibes out of this, especially the part where you're trying to [REDACTED] before you turn around and come back down the stairs.
I would say don't be afraid to make the Little Friends have more mechanical effects on the player. They don't necessarily have to be harsh and brutal -- even simple mischief can be deeply unsettling in a place like the Tunnels.
Please, please, please! make a longer game with this setting and style. The spareness of texture in the environment gives you some great potential to use texture to incredible effect (how you choose to interpret and implement that is up to you, and I'm sure it will make me deeply uncomfortable to witness it).
Great work y'all!