Trapped in a seemingly endless battle against a hoard of undead, what keeps Shuiyin Lu going are his memories of a girl. A girl he first met as a child and again as a college student… a girl with a mysterious past whom a sinister underground organization will stop at nothing to possess.
An action-comedy primarily set in a virtual world which features a bit of ecchi and romance along with a small amount of drama.
More Information:
aniDB (1, 2)
Crunchyroll
Wikipedia