1. Little Girl Magic is the magic aura that emits from little girls. (Lolicon is a related article.)
It's a magic so innocent and so sincere it beckons a true hero to keep it sacred.
In some cases a hero may need to defile the magic to keep it sacred.
Such is the way of LGM.
2. Some sort of radiation that emits from photogenic girls of ages 4-14.
It's nothing sexual, rather it's like hearing someone tell you that they love the smell of donuts, and the ideas and feelings it gives them, but that it has nothing to do with desire to eat those donuts.
"I'm no pedophile, but DANG, LGM alert!"