Hisaka can readily adapt an affable and polite persona to hide his true thoughts. On the other hand, he is also capable of saying blunt or even callous things if he considers it necessary. Wary and mistrustful, he has little empathy towards strangers, with the exception of children. Those who manage to win Hisaka's trust and loyalty are people he is ready to do anything for. To him, the world means next to nothing, for he exists solely to be useful to those he care about.
While responsible for much destruction during the ancient war, Hisaka never derived happiness from it, thinking that he was merely following the orders of his master. Nevertheless, he can be terrifyingly cruel and heartless when enraged, seeking to inflict as much pain as possible.
He also has a curious and scholarly streak, hence his usual introduction as a 'simple student of history and magic'. He likes to read about the times following the first Sahar War and tinkers with magic on his free time. However, nothing piques Hisaka's interest more than humanity itself. Due to his upbringing, Hisaka knows little of human interaction, attempting to learn more by observation. Therefore while most of the time he adopts a facade of politeness and sometimes reveals cutting distrust towards people, he is also prone to displays of childish naivety.