Phantom of Inferno

Kidzuki Rei is a female student who lost her parents since she was young. Being a grandchild of a Romanian vampire, Rei inherits only a quarter of a vampire bloodline, so she looks and lives a normal life like anyone else. She always keeps a wooden sword which belonged to her late father, a swordsman master, by her side to serve as her father's memento and to hone her skill in order to eradicate her parents' enemy, the demons.

Upon learning the information about demons, Rei transfers to a certain school where she meets a female student there. The student's name is Shindou Setsuna who defeats demons like Rei but as an exorcist. However, Rei and Setsuna don't get along due to their different natures.

Even so, they recognize each other's abilities while fighting against the demons and the became closer. Along with Setsuna, Rei starts to open her heart up for Yuka (Setsuna's older sister) and Touma (the sisters' childhood friend) as they work with each other.

Sadly, what awaits Rei is seemingly unending hell of pleasure...

At last, an all-out war is at hand.

The battle against the religious organization, The Fatal Answer (TFA), has entered its final phase, with CIRS and SORD preparing to send all of their troops into TFA's stronghold.

The battlefield soon descends into total chaos. Black rain pours down, civilians become desperate for water, and shots are fired at friend and foe alike. Not even the trenches are safe from the anti-aircraft guns TFA employs, the explosions bombarding the combat zone that the girls are tasked with invading. Such a feat is not unlike invading the depths of hell itself.

The underground base is quickly being suffocated by gunpowder, and the dark forest that surrounds the battlefield reeks with the stench of death. But both contain within them the faint yet tenacious flames of life; will those flames be able to withstand the harsh realities of war?

This must never, ever be repeated again...

The main character, Limua, is visiting a place on a guild mission.
She hears a mysterious voice.
A voice invites her to go through the cave, where she finds a sword.
When he picked up the sword, a soul named “Nero” appeared from it!
Demons becoming more ferocious, shadows operating behind the scenes in the capital, and the truth behind the Void Sword.
And an evil existence that threatens the world…
Rimua gets caught up in the vortex of the battle over the Hollow Soul Sword.