Board Thread:General Discussion/@comment-24155619-20140711014702/@comment-4010415-20140729010732

The idea of some kind of energy produced from within someone that helps to protect them and can even be used for attacks is a pretty common concept, and people actually believe in it in real life.

It has many names, both in real life and in manga/anime. Aura, ki/qi, chi, chakra, soul energy/reishi/reiatsu, etc and so forth. Soul Eater even kind of uses the concept in their own way and calls it soul wavelengths.