Sounds very similar to Shin Sekai Yori (From the New World)
Set in Japan, 1000 years after the modern era, Shin Sekai Yori follows
the life of Saki Watanabe, a girl from the town of Kamisu 66. In this
age, all humans possess powerful psychic abilities, and live an
idyllic life in agrarian villages. Saki gains her special powers at the age of
twelve and joins her friends Satoru Asahina, Maria Akizuki, Mamoru
Itou, Shun Aonuma, and Reiko Amano in enrolling at school to hone her
Two years later, as Saki and her friends reach
adolescence and develop relationships, Shun starts to distance
himself from the others and eventually goes missing.
Yakomaru's colony slowly ascends to power while conquering other colonies and wiping out the Giant Hornet colony, eventually
attacking Kamisu 66 with what is believed to be an Ogre that the
Monster Rats refer to as their "Messiah."
All the parts match including the human-like monsters building an army.
Very good show with all the build up to the surprising twist at the end!