Will is around the age of a highschool student, though his actual age is never specified. Will is originally from the one-shot Medical Magical, by Michiyo Kikuta. Kikuta decided to use him in Mamotte! Lollipop, as an examiner. Will comes and gives the young wizards a midterm. He kidnaps Nina Yamada, and the wizards must perform a series of tasks to get to her and be able to remain in the exams. Zero and Ichiare the only ones to pass, and he is so impressed with them, that he allows the other wizards who failed to remain in the exams as well.
Will also appears later in the manga and anime, when the Crystal Pearl is removed from Nina. In the manga, he congratualates Zero and Ichi on passing the exams, and as there first mission, has them stay with Nina another year to help her raise her new animal familiar. In the anime, he allows all of the wizards who assisted Nina in destorying the Black Pearl to pass the exams, and allows them to stay another year to help Nina raise her familiar as well.
We also see Will in the sequel, Madotte! Mamotte! Lollipop. We first see him after Nina swallows the Crystal Drop, and he gives the examanees of the Advanced Magic Exam the new task for the exam. He later comes to give another midterm, where the examinees must escape the hot springs that they have been trapped inside of. Nina is the first to escape, and so she waits with him for a while. She eventually gets upset, and since he cannot stand to see a girl sad, he turns her into a rabbit, and sends her back in the hot springs with Aquamarine, with a warning that if Zero and Ichi find out her true identity, that they will fail.
Near the end of the series, we see Will once again. He plans to help break the contract to stop the Advanced Magic Exams. Before he leaves to find Zero and Ichi, he has Nina make a wish on a magical item. This is important, as it gives Zero extra power, and helps them catch the shooting star, which is needed to break the contract.