First top 10 hit and Ishimura's graduation The single "Special Generation" was released on 30 March 2005, and ranked seventh on the Oricon Weekly Singles Chart. It was Berryz Kobo's first single to rank in the top 10, and their first to sell more than 20,000 copies. At that time, the group's average age was less than 12 years old. On 11 September 2005, it was announced that Maiha Ishimura would graduate from the group and Hello! Project to focus on her studies. Ishimura's graduation took place on 2 October 2005, on the last night of the Berryz Kobo autumn 2005 concert tour. 2006: Jiriri Kiteru The 10th single, "Jiriri Kiteru," was released on the 29th of March. It was ranked in sixth place on the Oricon Weekly Singles Chart, setting a new high for the group. 2007: Youngest concert at Saitama Super Arena In February 2007, Berryz Kobo made news headlines after it was announced that the group would be holding a concert at Saitama Super Arena on 1 April. The tickets for the two performances (a total of 20,000 seats) sold out almost two months before the premiere, and the group became the youngest act ever to perform a solo concert at the arena. At the time its members' average age was 13.8, with the previous record of 16.3 set by Morning Musume four years earlier. On 27 June, Berryz released their 14th single "Kokuhaku no Funsui Hiroba." It ranked fourth on the Oricon Weekly Singles Chart, becoming their highest-selling single. 2008: Awards and NHK Kōhaku Uta Gassen On the 12th of March 2008 the group released "Dschinghis Khan," their first cover song and, as of 2012, their highest- selling single. In October, Berryz Kobo participated at the 2008 Asia Song Festival in South Korea, representing Japan alongside W-inds and Anna Tsuchiya. Berryz won the festival's Best Asian Newcomer Award alongside the SM Entertainment group Shinee. On 12 December, they performed at Sharam Q's 20th anniversary concert at the Nippon Budokan. The group took part in the 41st show at Nakano Sun Plaza on 17 December, performing "Dschinghis Khan," for which they received a , awarded to the most requested song on the Cansystem cable radio network. The year ended with the group's debut at the 58th NHK Kōhaku Uta Gassen, an annual music show broadcast on 31 December. They performed a number together with Morning Musume and