Koujirou Sasahara, a high school student from a farming family, cultivates an aristocratic persona. He rides a goat named Kojirou—a namesake he bestowed—to school daily to evade walking. His borrowed butler, Hirose, attends him everywhere, sourced from wealthy classmate Kenzaburou Daiku. Sasahara's aesthetic includes non-prescription glasses and a tissue-crafted jabot integrated into his uniform.

His demeanor remains unwaveringly calm, seldom revealing anger. He exhibits gentlemanly conduct, such as offering his collar to Misato Tachibana after she accidentally breaks his glasses. He addresses Misato exclusively by her full name and displays indifference to her repeated mock firearm assaults, which mask her romantic feelings. Sasahara appears oblivious to her affections, as well as those of Mio Naganohara, who uses him as inspiration for her self-published yaoi manga.

Sasahara shares a childhood kendo history with Misato, whose frustration stems from his perceived lack of dedication and rejection of his aristocratic affectations. He also connects to Yoshino Naganohara through past kendo practice. As Drama Club president, he engages in non-sequitur activities like reading novels mid-conversation. His character contrasts with Daiku, who possesses genuine wealth but understates it. Sasahara appears consistently across official media, including the main anime's episode 21 ending theme, maintaining his eccentric traits and relationships throughout.