[I_am_Kami]

Originally Posted by Phibrizzo

You shouldnt take the name in a literal mean, its basically means "be the right hand of god" not superior to him in that context.

from the wikia

Touma's last name 'Kamijou' (上条) can be translated as "The person higher than God (La persona superiore a Dio)" (神上) in Japanese, from volume 14. Also, when he first meets Kanzaki she believes his name means (神浄討魔) in kanji as opposed to (上条当麻), which translates to "One that cleanses God