Shin Megami Tensei

Akemi Nakajima is a student in the "gifted class" in his high school. After being bullied and beaten by another student who a female student invoked, Nakajima uses his advanced computer skills to create the "Demon Summoning Program."
He summons demons to attack the two, but he gets carried away and ultimately kills them. Now sick with the power of the demon realm Makai in his hands, he summons the demon lord Loki. Realizing summoning such a powerful demon was a mistake, Nakajima sets out to reverse the problem he has created by any means.

Manga loosely based on Shin Megami Tensei. Plot features totally different characters and story.

Adaptation of Majin Tensei videogame.
The manga is set after the great war of the late 1990s as Japan begins construction on a new capital city. Earthquakes cause massive destruction and rumors of demons have begun to emerge. The protagonist receives a warning and a demon summoning program.