Albireo Ima is one of Nagi's former companions. He entered the fighting tournament during the Mahora school festival under the assumed name "Ku:Nel Sanders" and went largely unnoticed until he approached Asuna and was recognized by Evangeline. He appears to have information on not only Nagi's whereabouts, but also on Asuna's forgotten past. Albireo appears to be a perverted fellow, as his taste in making Evangeline wear costumes made apparent in recent chapters. He's also a cunning and shrewd man, akin to Nagi Springfield, and is considered as one of the two natural enemies which Evangeline has (he takes great delight in verbally tormenting her, even calling her Kitty), the other one being Nagi himself. Albireo Ima has a strong affinity towards gravity elemental magic.
An interesting fact revealed in the latest chapters is that Albireo has his very own Pactio card, which means that he, in addition of being a powerful mage, is also a Minister Magi. His artifact is a series of books, with an accompanying bookmark, that can be used to transform into a specific person, using all their skills and abilities. His present Pactio is with Nagi, but he has had at least ten contracts with other mages in the past, all of whom are dead.