Shuichi is a serious and polite boy with a generally submissive and unsure demeanor. He suffers from low self-esteem, often assuming others are more capable than he is, which makes him seem unreliable at first. He frequently blushes, suffers from cold sweats, and can be quick to make negative remarks or get defensive. Despite his timid nature, he is also level-headed and can adopt a stronger, more assertive attitude when the situation demands it. He holds the title of the 'Ultimate Detective'.