Shiragiku Oomura, a first-year student at Shin Koshigaya High School, joins the baseball team as right fielder wearing jersey number 9. She possesses long black hair and brown eyes. Originating from a kendo family, she previously achieved national championship status through rigorous training. Her parents allowed her to pursue baseball only after this accomplishment, fulfilling their condition.

Despite no prior baseball experience, her first practice swing launched an immediate home run off a pitching machine, revealing raw power. Yet she struggles to consistently replicate this success, underlining her novice status. Her swing mechanics adapt kendo techniques, generating notable power to drive balls deep despite frequent misses. This potential positions her as the team's primary long-ball threat.

She entered baseball out of genuine passion, approaching the game with visible enthusiasm. Observing Yomi Takeda's pitching alongside Nozomi Nakamura during team formation spurred both to join the club, aiming for the national tournament. Within team dynamics, Nakamura regards her as a rival due to her power-hitting capabilities, though Oomura remains mostly unaware of this perspective.

Assigned to right field as a developing player, her position reflects ongoing skill acquisition. Kendo discipline and physical coordination form the foundation of her baseball growth. Her progression integrates into Shin Koshigaya's broader team journey toward competitive success.