You see a flag near the exit, so you use your fingers to dig there. Most flags mark something, and this exit is pretty obvious, so there must be something under here. At least that's what you think to yourself as you dig.
You dig until you finally hit something. It's a bunch of buried old coots (くつ). They're in an underground room for old coots. One yells up at you, "Whatcha doing to our roof, ya whipper snapper?! Stop digging in our lawn!"