Sekai de Ichiban Atsui Natsu

is the second single by Japanese band Princess Princess. Written by Kyōko Tomita and Kaori Okui, the single was released by CBS Sony on July 16, 1987. It was re-released on July 1, 1989 as the band's eighth single, which became their second of five consecutive No. 1 singles on Oricon's singles chart. Background "Sekai de Ichiban Atsui Natsu" was originally released on vinyl in 1987 with "Vibration" as the B-side. As Princess Princess was relatively unknown at the time, the single did not chart. The song was used in the TV Asahi travel show . The song's original key is A. The song was re-released in 1989 as a CD single with the B-side being a re-recording of the song (known as the ). The CD jacket was designed to resemble an airline ticket; the first edition release was colored gold while the regular release was colored pink. The Heisei version of the song was used in the TV Asahi travel show . The song was remixed in the band's 1992 compilation album Singles 1987–1992.