Shiho Iwasaki, nicknamed "Shihocchi," was a founding member of idol group I-1club. She initially vied with Mayu Shimada for center position, securing the role after surpassing Mayu's sales under president Shiraki's stipulation—a result that prompted Mayu's departure. Despite achieving center status and becoming one of I-1club's most popular members, Shiho maintained her rivalry with Mayu. Her tenure as center later transitioned to Moka Suzuki.

When her team's sales underperformed against Moka Suzuki's unit, Shiho was stripped of her center position and transferred to Hakata, Fukuoka. There, she led the newly formed subunit NEXT STORM. Though perceived as a humiliating demotion, this move sparked a career rebirth. Shiho reclaimed center status in NEXT STORM, positioning the group as direct competition to rival units including Wake Up, Girls!.

During Wake Up, Girls!'s activities in Fukuoka, Shiho reunited with Mayu Shimada. She openly declared NEXT STORM equal to Wake Up, Girls!, cementing their rivalry ahead of the Idol Festival. Shiho's relocation to a Fukuoka subunit parallels real-life idol Sashihara Rino of AKB48, who similarly rose to prominence after transfer.

Shiho, 17, carries an unwavering competitive drive focused on Mayu despite their diverging paths. She has brown hair, gray eyes, and stands 1.63 meters tall.