“I'll definitely win it with you...”
POP 19.5: A-5 Love
Rei is somewhat shy and is shown to be rather serious and determined, like he is about the Magic Exam. He is also insecure about his magical level and being shorter than Itsuki.
Rei wishes to study abroad in the Magical World because he wants to take the magic exam. However, to do so, he needs another wizard or witch to be his partner, and there are no other wizards or witches in the Human World. When Itsuki finds out about this, she hunts down Rei and tells him that she will be his partner. Rei, however, doesn't want Itsuki as his partner because taking the magic exam isn't a joke to him, so he runs away with his friends.
Later that evening, Rei is training with Zero, his father, and Ichî, Itsuki's father. Rei is trying to learn "Destructive Magic, Broken Storm", but the spell is too much for him to handle. He then watches his father and Ichî and feels a bit discouraged because of his level. When Rokka and Itsuki come to pick up Ichî, Itsuki once again declares she'll be Rei's partner and he states that she is the last person he'd want to partner with.The next day, while Rei is at school, Itsuki shows up again, wanting to show Rei her many talents so he'll accept her as his partner. Rei ends up snapping at Itsuki, getting angry at her because she is five years younger than him and is taller, better at sports and studying than him. He also tells her that he hates her. Itsuki, however, only shouts at Rei and takes him to the roof. When Itsuki tells him that they're going to fly down together, Rei says he doesn't want to do it, but she only hugs him and tells him that he'll protect her. Itsuki only ends up falling off the side of the school, as she hasn't learnt any Defensive magic, and Rei quickly saves her using his advanced Destruction magic. Rei then tells Itsuki that he will definitely win the Magical Exam with her as his partner.
Later, when his little sister Mina cries over Rei leaving, he tells her if she'd just said she doesn't want him to go, then he won't.