In a world similar to the European Middle Ages, the feared yet revered Holy Knights of Britannia use immensely powerful magic to protect the region of Britannia and its kingdoms. However, a small subset of the Knights supposedly betrayed their homeland and turned their blades against their comrades in an attempt to overthrow the ruler of Liones. They were defeated by the Holy Knights, but rumors continued to persist that these legendary knights, called the "Seven Deadly Sins," were still alive. Ten years later, the Holy Knights themselves staged a coup d’état, and thus became the new, tyrannical rulers of the Kingdom of Liones.
Based on the best-selling manga series of the same name, Nanatsu no Taizai follows the adventures of Elizabeth, the third princess of the Kingdom of Liones, and her search for the Seven Deadly Sins. With their help, she endeavors to not only take back her kingdom from the Holy Knights, but to also seek justice in an unjust world.
Di dunia yang serupa dengan Zaman Pertengahan Eropah, Satria Suci Britannia guna kuasa ajaib yang kuat untuk melindungi Britannia dan negaranya. Namun sebahagian kecil Satria ini dituduh membelot tanah air and pemerintah Liones mereka. Kemudian mereka ditewas oleh Satria Suci, tapi khabas angin mengata satria legenda ini, “Tujuh Dosa Maut”, masih hidup. 10 tahun kemudian, Satria Suci melakukan coup d’etat, dan menjadi pemerintah Negara Liones baru yang lazim.
Siri animasi ini mengisahkan pengembaraan Elizabeth, puteri ketiga Negara Liones, dan pencariannya terhadap Tujuh Dosa Maut. Dengan bantuan mereka, dia berusaha bukan saja untuk ambil balik negaranya daripada Satria Suci, tapi juga untuk mencari keadilan dalam dunia tidak adil ini.