Stocking is a character from Gainax’s latest anime series “Panty and Stocking with Garterbelt.” Stocking is the younger of the anarchy sisters. They were thrown out of heaven due to their bad behavior. They are sent to Daten City (presumably earth?) where they battle strange monsters called “Ghosts” which besiege the city.
Their powers are based on their ability to transform their clothing into weapons. Stocking in particular is able to transform her “stockings” into swords.
Sisters Panty and Stocking change costumes very frequently in the show. This is Stocking in her angel form.