Negima!? Magister Negi Magi Episode 8: Professor, Please Make Us Adults.
Episode 8 of 26 of Negima!? Magister Negi Magi, aired November 22, 2006, 25 minutes. Available with English subtitles and dub where released.
Episode summary
The Narutaki Twins try to prove to everyone that they are adult-like rather than children. Meanwhile Negi and his partners go to Library Island to research a gem left behind from the fairy incident.