You are part of the Phantom Thieves and you all were currently battling against the shadow version of Marie Anto. While the battle was going in your favor, Shadow Marie used a powerful attack that blinded everyone. When your vision clears, you see all the other phantom thieves standing by Shadow Marie.

You looked confused for a moment before noticed that your friends all had a glassy expression on their faces

Makoto: Lady Marie, we shall defend you until our last breaths. I swear myself to you, oh Devine and Wonderful Queen. She says with a smile on her face as she dropped to one knee in front of Shadow Marie, like a knight swearing themselves to true royalty