 LiSA made her solo debut on April 20 , 2011 with the release of her mini @-@ album Letters to U by <unk> under Sony Music Artists . The songs on the album were composed by <unk> and major artists , and she composed the first song " Believe in Myself " ; she wrote the album 's lyrics . On November 12 , 2011 , She made her first appearance in Singapore at Anime Festival Asia , Southeast Asia 's largest anime and pop culture convention . She released her first solo single " Oath Sign " on November 23 , 2011 , which was used as the opening theme to the 2011 anime series Fate / Zero . The single peaked at No. 5 on the Oricon weekly charts and was certified gold by the Recording Industry Association of Japan ( RIAJ ) . 
