Megumi Ooumi is a 14 year old pop star, and The Keeper Of The Book to a 6 year old mamodo Tio. She is often seen in video games or doing concerts but despite all this remains a normal girl.

She has a very kind-hearted personality, and sees Tio like a little sister, often calming down her fits of rage and helping explain the world to her.

Megumi first met Tio when she found her injured on the docks. At first, Tio had kept harshly to herself when they'd first met, saying that Megumi would only get hurt helping her fight off mamodo. They eventually started to get along and Tio came to trust Megumi.

After being helped by Zatch and Kiyo, Megumi saw them as friends, like Tio, and swore that one day they would return the favor.

After Clear Note returned to the Mamodo World, Megumi can be seen visiting Zatch and Kiyo with a lonely face, having missed Tio.

A month after the battle to decide the Mamodo King ended, with Tio placed 5th in the battle overall, Megumi received a letter from Tio and tearfully read it.

(Source: Wikipedia and Zatch Bell! Wiki, edited)