When I Put up the Strongest Barrier in the Country, It Became Too Peaceful and I was Banished. They Did Know That That Barrier isn't Permanent, Right?

A young man, Shield, can only use the beginner magic [Barrier] and has been looked down upon. Despite putting up an ironclad barrier to protect the country, he is deported due to his fiancée's tricks. However, before he knew it, he had subjugated the strongest dragon (a young girl), was courted by beautiful women from other countries, and was being followed by a group of brutal demons!?