Lavi

A cheerful Exorcist of mixed race, who aims to become a Bookman and is working along the Black Order just to be close to the events that must be seen. To help him, he developed an incredible memory: he is able to memorize every single aspect of something he saw.

His anti-Akuma weapon is a size-shifting hammer, which he calls Ōzuchi Kozuchi or Nyoibo. It can grow or extend. The weight increases with its size, but since Lavi is the conformer, the weight does not effect him; however, it does to everyone else. His hammer can also summon several "judgments" with kanji possibly representing the classical elements that can be used individually or combined. However, between some of the seals are question marks. This probably means that Lavi has some seals that he has yet to learn from his Innocence.

(Source: Wikipedia)