In 2004 Berryz Kobo was formed, with the intention of rotating the kids throughout the unit. Yajima didn't make the original pick, and the idea was eventually dropped. The remaining kids ending up forming °C-ute in 2005. Despite not being the oldest, Yajima still became the group's leader. The group didn't make its official debut until late in 2006, with their first official single released in February 2007.
Aside from leading °C-ute, Yajima is also the sub-captain of Little Gatas, the Hello! Project Kids futsal team. She's 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.
In 2008 Maimi was selected to be a member of Hello Project's new unit High King