Digital Devil Monogatari: Megami Tensei

You are Akineki Nakashima, a 17-year-old Japanese student and computer freak. You developed a program that allows you to communicate with demons via your computer and to summon them. To test your new program, you summon the Norse god Loki. Unfortunately, the newly summoned god kidnaps Yumiko, a girl who studies together with Nakashima. Japan becomes infested with demons, and now it’s up to you to traverse the mazes of the demon realm and to rescue Yumiko.