It has just been announced at Hello!Project's 15th anniversary concert that Mano Erina will be graduating from Hello!Project on February 23rd during her upcoming final tour. The last concert will be held at the Nakano Sun Plaza.
Mano joined Hello!Project in 2006 as a Hello! pro egg before being added to the group "Ongaku Gatas" in 2007. One year later she graduated and became a soloist releasing her first indie single "Manopiano" in June. The following year she made her official debut in March of 2009 with the single "Otome no Inori"
source - http://forum.jpopmusic.info/viewtopic.php?f=16&t=5915
*update* - now on H!P's official website http://www.helloproject.com/news/1207211800_mano.html