Sumi had no option for surviving other than killing that zombie who was right above her.
The zombie had pinned Sumi down on the ground and tried to eat her. He was desperately trying to get to her and bite her but her hands kept him from doing that.
But, she couldn't hold that zombie for too long. Her hands were tearing up. She was losing the remaining strength in her body.
On the other side of the room, Kingslayer and Ryuga were trying to get to Sumi to help her. They were pushing the door with all their might. Even if their hands were crying out in pain, they kept on going all in. To save Sumi, they both were going all out.
Toshi was fighting the big waves of zombies who were coming at him all by himself. His silver sword and hair both got coved with the red lustre of the blood. That whole room had become a bloody mess.