Lero

Lero is excitable, anxious and intensely loyal to The Millennium Earl. He becomes nervous when members of the Noah Family ignore the Earl's instructions and frequently protests Road Kamelot's habit of taking him without permission. His characteristic speech pattern adds "Lero" to the ends of his sentences.

Around enemies, Lero can display a more malicious streak, taunting Exorcists when he believes he is safe. That confidence disappears quickly when he is personally threatened.

Lero is capable of independent flight and can transport people far heavier than himself. Road commonly rides him like a flying broom, while the Earl also uses him for aerial movement.

He can act as a conduit for the Earl's powers, including summoning Akuma and producing powerful attacks. Lero can also facilitate the manifestation of the Earl's large broadsword, although the Earl is capable of summoning the weapon without him.

Lero additionally performs practical functions for the Noah Family, including transportation to Noah's Ark and countdowns used to coordinate Akuma self-destruction.

Lero appears from the beginning of the series as part of The Millennium Earl's arsenal. He helps the Earl summon Akuma and escape encounters, establishing him as both a supernatural tool and a sentient servant.

Road Kamelot later takes Lero into Rewinding Town, where he accompanies her confrontation with Allen Walker and Lenalee Lee. Lero tries unsuccessfully to keep Road from revealing information the Earl would prefer hidden and helps her escape once the battle turns against her.

He continues accompanying the Noah during the struggle over Noah's Ark. His mobility and connection to the Earl make him a recurring support figure whenever the Noah Family needs transportation or access to the Ark.

The Millennium Earl is Lero's owner and the person to whom he is most loyal. Lero assists with transportation, Akuma summoning and the Earl's weaponry.

Road Kamelot frequently takes Lero while the Earl is asleep and uses him as a flying umbrella. Lero protests her behavior but has little ability to stop her.

Allen Walker repeatedly encounters Lero through his battles with the Noah Family. Lero regards Allen and the other Exorcists as enemies.