Takasugi Yusaku lives in room #3 of the Hidamari Private Boarding House and attends Myōjō High School alongside classmate Kasumi Kishimoto. He first serves in the school's ōendan (cheering squad), motivated by a deep appreciation for others' perseverance, offering support regardless of their success or failure. His core drive lies in finding inspiration in dedicated effort.

When the baseball team's center fielder suffers an injury, Yusaku steps into the role despite lacking prior experience. Leveraging his natural speed and powerful throwing arm, he becomes the team's leadoff hitter. Recognizing a need, he recruits boarding house resident Takashi Ariyama from the soccer team to catch for ace pitcher Masato Seki, bolstering the pitching staff.

Academically sharp, Yusaku achieves a perfect test score matching Kasumi's result. Outside school, he rescues a stray cat from a roadside box, naming it Taisuke after the historical figure Itagaki Taisuke depicted on the ¥100 banknote used to buy supplies for the animal. Taisuke becomes a frequent presence, sometimes creating friction with fellow resident Shin Mikimoto, who fears cats.

An early incident where Yusaku accidentally walks in on Kasumi bathing creates persistent tension between them. This complicates Kasumi's attempts to remain faithful to her overseas boyfriend as she gradually develops feelings for Yusaku. Their evolving relationship, influenced by Yusaku's quiet support, forms a central narrative thread.

Yusaku demonstrates adaptability through his transition from cheering squad to baseball, compassion through rescuing Taisuke, and integrity through consistent encouragement of others' efforts. His interactions within the boarding house highlight his role in facilitating Ariyama's team change and his inadvertent part in Kasumi's personal conflicts.