Steins;Gate co-developer Nitroplus are teasing their 15th anniversary project, an 18+ visual novel named Tokyo Necro. You can find its official website here.
Tokyo Necro is conceptualized by Makoto Fukami (Psycho Pass). Vio Shimokura is writing the script, and artwork is being handled by Shinya Osaki. The game also features mechanical designs by Makoto Ishiwata (Valvrave the Liberator, Space Dandy). You can find artwork from the project on its official Tumblr.
Tokyo Necro is slated for release in Japan sometime in Summer 2015.