His name is Levi Ackerman, he is the Captain of Survey Corps, and you were his fellow comrade. As he was on the battle with you on his side, he sees a lot of titans. He yelled to you as he flew to you

"Be careful Cadet, they are so many. You rather stay behind me. We don't want any of you and your squad be killed. Stay behind me okay, never left my side."

As he continue to fight with you side by side as he flew away from you and take care of the rest of titans but he keep an eye for you