Yakumo Ishii (石井 八雲, Ishii Yakumo) is an examinee in the Magic Exam as well as the Advanced Magic Exam. He specializes in Transformation Weapon Magic, which enables him to turn any object into a weapon.
A notably distinguishable characteristic of Yakumo’s is the fact that he speaks in a Kansai dialect. Apparently Yakumo falls in love very easily, as is the case when he first meets Nina Yamada. Yakumo also enjoys playing sports.
In Magic Cram School, once a month students would challenge each other, but Yakumo and his partner Nanase Akatsuki would always tie with Zero and Ichî, sparking a rivalry between the two pairs. While Zero is clearly amazed by Yakumo’s magical abilities to turn any ordinary object into a weapon, in Cram School Ichî comments that it is “lame”, leaving Yakumo with a long held grudge against Ichî.
Yakumo and Nanase are both examinees and track down Nina, who is now known by many to have swallowed the Crystal Pearl. Upon seeing her, Yakumo is enamored, and rather than killing Nina for the Pearl as some students aim to do, Yakumo aims to protect Nina until the exams end like Zero and Ichî aim to do.
Yakumo asks Nina out on a date and he and Nanase end up kidnapping Nina and taking her to the beach. While on the beach Yakumo asks Ichî if he cares for Nina, suggesting the two have a sibling-like relationship. After this Ichî broods over how much he hates Yakumo.
Nanase is often jealous of Nina and messes with or tries to hurt her, and in response Yakumo is always outraged, scolding his partner for having done so and telling him that it is “against the rules” (which he made up) to hurt Nina.
In a side story, Yakumo is seen to have a crush on another girl named Kotone, though their relationship is threatened when a jealous Nanase interferes. Seeing how much Yakumo clearly cares for Kotone, Nanase explains to Kotone that he was jealous and that Yakumo really likes her.
In the second series, Yakumo comes back with Nanase to yet again participate in the exam. In the chapter where Nina is sent into the future by Rill, it is revealed that Yakumo ends up marrying Kotone and having two children with her.