There are 6 Owls to track down and return to the Owl Forest in Menancia for Tales of Arise. These are completely optional but offer multiple Trophies/Achievements while granting you rewards mostly in the form of cosmetics.
Owl #16 - Overseer Hill
Head to Overseer Hill and go south to reach the Camp there. From here, you can head south to reach the fishing spot where you’ll find the Owl perched on the wall to your left, this one will hand over the Red Tropical Corsage.
Owl #17 - Traslida Highway
Head across the bridge to reach a farm and look in the wheat field close to the stable to find this Owl. You’ll obtain the Devil Wings for discovering this Owl.
Owl #18 - Tietal Plain
Head to the southeast of the plain and cross under the large arch overhead. Turn around and face the other side of this to find the Owl who will present you with the Giggle Glasses.
Owl #19 - Viscint
Make your way to the east of the Inn and you’ll unlock a Fast Travel. The stall directly to the east of this has a large blue pot where you’ll find the Owl, this one hands over the Halo.
Owl #20 - Autelina Palace 1F Kitchen
Head to Autelina Palace and enter the Kitchen found in the room to the right located in the northwest of the floor. Once there, look on a shelf on the western wall to locate the Owl and obtain the Crown.
Owl #21 - Talka Pond Road
Exit to Talka Pond Road from Viscint and head to the wall on your right. The Owl is perched on top of the wall here (close to the Boars) and will hand over the Devil Tail.