DemiKids

The year is 200X. Jin, Akira and Lena are three child hood friends who like mysterious things. One day in the library, along with the mysterious transfer student Ami, they find the "Akuma Compendium". They chanted an incantation in the book and, to their surprise, devils appeared. Ami then told Jin and Akira that they are the Devil Children that will decide the fate of the world. She hands them their Devil Risers. The group then pass through the "Door of Time" to the land of Valhalla where they fight an evil ruler known as Imperius who plans on conquering all of the world. The Nakama of Jin is Rand, a Sol Lion, and Akira's is Gale, a Hylon.
Source: ANN

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.