Kenji Ninomiya is a middle school student who serves as the president and sole member of his school's calligraphy club. His dedication to this solitary pursuit means he is often found practicing on the school rooftop, a quiet space that suits his reserved nature.

In terms of personality, Kenji is characterized as being quiet, aloof, and somewhat slow on the uptake. He has a tendency to be forgetful and spaced out, which makes him appear oblivious to the world around him. Despite this detachment, he possesses an honest and simple demeanor. His primary passion lies in his calligraphy brushes, and his artistic practice is deeply personal; he only engages in calligraphy when he feels genuinely inspired.

Kenji's role in the story is primarily defined by his relationship with Yurie Hitotsubashi, a classmate who has harbored an intense crush on him since they entered middle school. Much of the gentle humor surrounding his character comes from the fact that he is completely unaware of Yurie's feelings. His inspiration for calligraphy frequently revolves around her, though it takes him a considerable amount of time to realize this connection. Over the course of the narrative, this dynamic slowly develops, culminating in him becoming Yurie's boyfriend by the end of the series.

Beyond his artistic habits, Kenji is also known to perform calligraphy work for the Raifuku shrine, lending his skills to the local spiritual community. His notable abilities are entirely focused on his artistic craft, which he pursues with a quiet, single-minded devotion that defines his interactions with the world around him.