OneeChanbara: Kurenai

The dead have risen to feast on the flesh of the living, and just when it seems that all hope for humanity has been lost, bikini girls with machine guns take one last shot at saving mankind from certain extinction. In the near future, a deranged scientist named Sugita has conducted a series of experiments intended to reanimate the dead. Unfortunately for the entire population of the planet, these experiments were a resounding success. Now, as a massive, shambling army of the undead launches a bloody war against their living counterparts, wandering beauties Aya and Reiko team up to destroy every last zombie in sight. Unfortunately, Aya's sword-wielding schoolgirl sister Saki is in league with the nefarious Sugita. When Aya discovers that Saki has killed their father, she vows to take brutal revenge against her murderous younger sibling. Meanwhile, the zombie population is growing at an alarming rate. (Anilist)