Arata has a carefree and cheerful personality, usually bantering and teasing others even in dangerous situations. He is also noted to be very perverted, often finding himself in risque situations or confessing his desires towards a girl. Usually, this is by complete accident, but he simply rolls with it and lets himself enjoy the situation without getting worked up about it. During these situations, he usually quotes: "Thank you for the treat" or something to that effect. This often earns him a scolding from Lilith and scorn from Mira Yamana, the Top Seat of Grimoire Security, who calls him filthy or impure. Other girls such as Levi, Akio, or Lieselotte don't particularly mind and often goes along with his remarks. However, he knows where to draw the line, as he refuses a kiss from Yui because that is only for "when we're closer". In times of need, Arata can become very dependable. Arata is very calm under pressure, in both perverted and dangerous situations. His natural way of thinking allows him to make rational decisions and develop solutions to problems that otherwise others would panic too. Arata cares very deeply for others, especially his friends. He is willing to risk his life and become stronger to save those he cares about, such as Lillith, Yui, Lieselotte, etc.
Despite his perversion, Arata has a mature view of relationships. For instance, he refused a kiss from Yui due to believing that was something they should do when their closer. Furthermore, as seen in the Ova, Arata will not take advantage of girls who are vulnerable to physical needs, showing he has some respect for women.
There are two known instances that can cause Arata to lose his cool. The first is Kasuga Hijiri, who is his entire motivation for becoming a magician and his driving force for most of the story. Lieselotte was able to shake him mentally by offering information on her whereabouts, and when the two of them finally do meet he single-mindedly tries to take her back. The other is someone disappearing due to his own powerlessness, a trauma developed by Hijiri's apparent "death". The first time this happens, he triggers Astral Trinity's awakening to prevent it.
During the Sky Library Arc, Arata admits that the Trinity Seven members are essentially as important to him as Hijiri is, showcased by one of his very rare shows of anger towards Abyss Trinity for hurting Akio.
Following his transformation into a Sword Magus, he has displayed signs of agressiveness occassionally, catching the notice of both Akio and Selina.