Sekai (世界, World) is a song by Chara. It was released as the first single from her album Union on September 13, 2006. It debuted at #24 on the Japanese Oricon album charts, and charted for five weeks. The song was used in commercials for the NEC brand 'Foma N702iS' cellphone. Chara wrote the song in 2005. The main guitar chords in the song were recycled from the song Ongaku (音楽, Music) from her 2005 independently released album Something Blue. She wrote "Amai Tori" (甘い鳥, Sweet Bird) in the style of Stevie Nicks. The B-side "Anata" (あなた, You) is a cover of 's 1973 debut single.