miwa released her first album "Guitarissimo" on April 6, 2011 (was scheduled to release a week earlier on end of March but was delayed due to the Tōhoku earthquake and tsunami and its aftereffects). The charts performance was miwa's best overall: the album reached No. 1 in the Oricon's album charts, making miwa the first Heisei period-born solo singer to reach a No. 1 on the album charts in the history of the Oricon.