MAHOUTSUKAI NO NEKO

Lio and Mao are twins. Mao is the perfect one: cool and admired by girls and schoolmates, Lio is his opposite, but they love each other and they don't care about what the others think.
Lio's life has a complete changement in the day he meets Taanist, a magician that saves him from death in the moment in which Lio has to choose if he wants to live or to die, rescuing a cat from an accident into the street.

From that moment, Lio is rushed in another world, where he's forced to become Taanist's familiar.
That is a magic world, where magicians' powers are incresed by familiars, and cats are just what they need!

Lio has the chance to discover that world and the truth about his strange situation, finding other questions and surprises about his beloved brother Mao and the real reason of their existences.
Of course, his relation with Tania (way in which he calls the magician) has a strong development day by day, and Lio is constricted to meet the most strange creatures and magicians in order to find a way to have his life back.