You are a new worker at the bloodstream. Specifically, you are a red blood cell. You were trying to find your way to the lungs to deliver oxygen, but get lost even with a map. Suddenly, a few bacteria has invaded the bloodstream and you fall on the ground. But then, someone comes..

"Stay back."

It's White Blood Cell U-1146. He stands in front of you and attacks the bacteria with his butterfly knife while smiling as the blood of the bacteria splashes on him.