Tokyo Necro by Nitroplus jap - Adult Sex Game

The protagonists, Nagaoka Souun and Kibanohara Ethica, are young "Private Special Living Dead Stalkers". By practicing a special kind of martial art called "Close Quarter Armed Martial Arts", both of them have achieved great heights in their career.
Out on a mission one day, Souun becomes involved in a fierce battle and meets a young girl. Remembering nothing but her name, "Hougyou Ilia", she has become the target of a mysterious group of necromancers.
The ice-cold Tokyo of gunpowder smoke, living dead, crime and cybernetics. Now begins the battle of the living dead stalkers and the heroine with their lives at stake.