"Sen to Rei" (Japanese: セントレイ^?, "1000 & 0") (Japanese pronunciation: [sentoɺei]) is a song by Japanese band Sakanaction. It was released as a digital download on November 12, 2008, and on December 10 was released as the band's first physical CD single.

Shin-shiro was the band's first album after joining the main Victor Entertainment roster and signing a contract with management group Hipland Management. In Spring 2009, the band moved to Tokyo from Hokkaido. The album was primarily created by band members in vocalist Ichiro Yamaguchi's apartment in Kawasaki, Kanagawa.

Before the band had moved to Tokyo in the spring of 2009, the song "Adventure" was originally planned to be the leading single from the album, in the place of "Sen to Rei". "Adventure" was written by Yamaguchi to consciously give the band a more accessible sound. Yamaguchi had intended to make music that blended underground and "high entertainment" pop music sounds on the band's first two studio albums, Go to the Future (2007) and Night Fishing (2008), however found that the band was predominantly seen as more underground than pop. Yamaguchi realized that in order to balance underground and "entertainment"-based pop music styles better, he needed to add more entertaining aspects. Yamaguchi considered "Adventure" the first step towards this sound, and challenged themselves to develop their popular sound more in "Sen to Rei". "Sen to Rei" became crucial to the creation of Shin-shiro, as the band created the entire album in response to the song, considering what aspects of Sakanaction's sound should listeners who had heard "Sen to Rei" hear, in order to experience all of Sakanction.

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