Red Blood Cell is being chased by a germ! The one to come to the rescue is a masked Monocyte. Apparently, they are also part of the White Blood Cell family and a type of Immune Cell. There’s no way Red Blood Cell could be attacked by bacteria twice in one day, but she encounters another one on her way to the nasal cavity. The germ turns out to be Staphylococcus Aureus. They usually just exist on the skin and pores. But this time, they have a secret plan. What could it be?

"We have detected life-threatening damage!" Hearing of this emergency, White Blood Cell (Neutrophil) rushes to the blast area. But there, he finds no traces of the blood cells he's supposed to protect! Due to massive bleeding, a huge amount of blood cells have already been flung outside the wound. And the bleeding continues... The situation grows more dire every second, but to protect this world and to save her friends, Red Blood Cell continues to deliver oxygen with Li'l Kouhai Red Blood Cell. Their world is on the brink of destruction... What kind of fate lies ahead for the cells?