Davidia and the Knowledge Tree

There's a deepening mystery that the world's written language kept disappearing for good, with no explanation. 

Schoolgirls Davidia and Slirander catch a perpetrator finger-licking his way through a book, making the words disappear, and were puzzled. They spring into action to find the cause of the destruction and find themselves on a journey, trying to solve the puzzle of the disappearing words. 

A Moonah tree whose leaves represent the letters of the alphabet help them on their journey, transforming them to strange and mysterious places where they find the fateful pit of lost letters, but not before they had to escape the traps set for them by the different keepers of the alphabet who hung tenaciously to their letters. All the while they had to outsmart their adversary, the enemy who had stolen the written word from the world. 

Who was this character? Were the girls successful in their mission to save the language of the world?