Shin Megamitensei

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.