is a Japanese singer and actress. She was a member and the leader of Cute, a girl idol group within Hello! Project.
Yajima first joined Hello! Project in 2002 as one of the fifteen children chosen from the Hello! Project Kids auditions after performing "Momoiro Kataomoi" by Aya Matsuura. She debuted the same year in the movie Koinu Dan no Monogatari, taking on one of the main roles as an antagonist. The following year, she joined the first of the kids' groups, ZYX, which released two singles.
In 2004, Berryz Kobo was formed, with the intention of rotating the girls throughout the unit. Yajima did not make the original pick, and the idea was eventually dropped. The remaining girls eventually ended up forming Cute in 2005. Despite not being the oldest, Yajima still became the group's leader, after Erika Umeda turned down the role. The group did not make its official debut until late in 2006, with their first official single released in February 2007.
Aside from leading Cute, Yajima became the sub-captain of Little Gatas and the Hello! Project Kids futsal team. She was also considered to be one of the fastest runners in all of Hello! Project, often coming first in the running events at the annual sports festivals and listing running as one of her hobbies.
Yajima also co-hosted Cute's weekly radio program, Cutie Party. She took over the role when Megumi Murakami left the group.
In 2008, Yajima was selected to be a member of Hello Project's new unit High-King. Yajima and Fukuda Kanon appeared in the movie Fuyu no Kaidan (Winter Ghost Story), released in Japan on May 23, 2009.
Cute disbanded following their final concert at Saitama Super Arena on June 12, 2017. Yajima had announced earlier, via the group's blog, that she planned to pursue an acting career.
Maimi's younger cousin, Akari Takeuchi, is a former member of ANGERME, another girl group within Hello! Project.
On November 8, 2022, she announced her marriage with actor Ryosuke Mikata. On March 25, 2024, she announced her first pregnancy. She gave birth to her first baby in July of the same year, and announced her second pregnancy in June 2025, and gave birth to her second baby in November 2025.