S1·E79 The Offense and Defense Assasin! Shun's Secret Chain!

Koga, Yuna, and Souma advance through the first path while Shun stays behind to deal with the enemy reinforcements. However, the Secondary Pallasite Surtr blocks their path enveloped in a defensive barrier that seems impenetrable, until Shun catches up with them and realizes the secret behind the enemy's trick.