Kōjirō Sasahara cultivates an aristocratic persona as a high school student despite his farming family background. He consistently displays refined manners, remaining calm and collected, rarely showing visible anger, and formally addresses others, such as using Misato Tachibana's full name. Sasahara wears glasses purely for aesthetic reasons, not needing vision correction, and accessorizes his uniform with a jabot made of tissues.

He travels to school riding a goat named Kojirou, sharing its name, reflecting his eccentric tendencies. His butler, Hirose, regularly accompanies him, attending to his requests; Hirose is lent to Sasahara by his wealthy classmate Kenzaburou Daiku. Sasahara naturally engages in non-sequitur activities during conversations, like playing a Game Boy or reading a novel, without intending to tease.

Both Misato Tachibana, a childhood friend who practiced kendo with him, and Mio Naganohara admire him romantically. Misato exhibits a tsundere attitude, often reacting to embarrassment by shooting him with simulated weapons, attacks he remains unfazed by and seemingly oblivious to. Mio expresses her crush through shyness and frequently includes him as a subject in her yaoi manga under a pseudonym; Sasahara appears unaware of her feelings too.

His early appearances include notable incidents, such as making a memorable entrance at the school opening ceremony on his goat, leading to reprimands from Misato. His presence becomes less frequent in later segments. Sasahara holds the position of president in the Drama Club, though specific activities or contributions are not detailed.

His farming family background contrasts with his self-styled nobility. His friendship extends to Yoshino Naganohara, Mio's sister, with whom he also practiced kendo. His interactions generally lack significant development or backstory elaboration across official media.