Here are some of the planned sequels!
2) Teen from the first book chases a living weapon made by angels, and in saving said weapon's little sister, expands his harem by well over 9000.
3) Teenage Hero battles his teachers for ownership of an Evil Weapon
which turns into what appears to be
an Evangelion when its satisfied with the fighting...oops!
4) Teenage Hero pursues an omnisexual pervert who wants to make a giant halo appear in the sky.
5) Breather Novel. The Teenage Hero, the above pervert and sister to a living weapon must stop a guy from waking up his Apocalypse Maiden
6) The Teenage Hero must stop a monster from making all the urban legends in the world a reality by the consequence of its existence. Involves a lot of former background characters.