There is a tall icy mountain in the dessert near the town.
The dessert heat normally keeps all the plant monsters away and naturally protects the town.
A runaway miner from Nostrum decides to mine ice from the mountain to sell in town for a living, but accidentally unleashes plant monsters living inside the mountain.
Only the peak of the mountain is cold. The inside is very mild due to a combination of the dessert heat and the cold peaks. The plant monsters have been thriving inside the mountain for years.

After releasing the monsters, the miner wants to quit mining.
"Why do caves always have something living inside them??"
"Same reason why forests do."
"You're the worst miner ever."

The ice dungeon is mild at the bottom and cold at the top.
So the bunnygirls and shotas mostly hang out at the lower floors.

How to "funnel" the player back toward town after finding Lilly?
Use the player's curiosity to entice them back... 
And also place the fairy teleport INSIDE the town. (in fact that might be a good idea for most towns)
Maybe after visiting the dungeon the shotas leave and the player wants to see what they're doing back in town.

So add a town-state before the player has the laser ability.
The town's people mention the miner seeking ice.
The miner mentions how this will be so much better than mining iron back in nostrum. No dragons here.

And maybe add an end town-state based on time-of-day that shows the daily routine of the shotas.
Day:				Prepare for their duty to visit the Bunnygirls.
Evening:		Shotas with bunnygirls.
Night:			How do the shotas act back at home after playing with bunnygirls?