Terashima Yufu 9-sei performed in the early lineup of idol group BiS (Brand-new Idol Society) alongside Pour Lui and Hirano Nozomi. During 2012 group activities, she participated in a conceptual prank culminating in the release of "IDOL." This involved filming a deceptive promotional video with conventional maid outfits and cheerful choreography, deliberately contrasting the actual heavy metal-inspired single and its subversive anti-idol music video.

Her signature trait was a constant, wide smile recognized as a trademark expression. This persisted during performances and promotions where other members adopted serious or confrontational personas. In the grim "IDOL" music video—featuring smeared makeup, minimal color, and members paraded on crosses—Terashima visibly suppressed her natural smiling demeanor while it remained a noted aspect of her presence.

Within the anime adaptation "Backstage Idol Story," Terashima Yufu 9-sei appeared as a character during ensemble segments depicting the group's off-stage interactions. These included candid backstage discussions about idol challenges such as disruptive fans, personal logistical issues like worn-out underwear, and menstruation during performances. Her participation occurred in these ad-lib talk segments focusing on the group's collective dynamics.