Hello There!

A long time ago, monsters from another world invaded earth, and we were horrified to realize that our guns and bombs barely fazed them. Seeing how strong they were, we were left with no choice but to hide and hope for the best. We created cities with huge walls surrounding them, thinking that it will keep the monsters out, but it rarely did.
One city, though, in the middle of a large forest, hasn't seen a monster in 10 years. There are multiple theories on why this may be, but they would never guess what is actually keeping them safe..