A Certain Magical Index, Vol. 11 (light novel) — Kazuma Kamachi

Tokiwadai Middle School--a place bathed in the envious gazes of all the schoolgirls in Academy City. Every single one of its female students is a proper young lady, and none more so than Mikoto Misaka. Kuroko--a Level Four teleporter and a member of Judgment, the organization that preserves public order in the city--knows this all too well. She invites her darling Misaka out to go shopping, but that's just the beginning of what ends up being a very, very long day, one in which she sees Misaka's true form and may wish she hadn't...