"Week!" is the ninth single of Do As Infinity, released in 2001. The B-side of this single, "Tsuredzure Naru Mama ni", is the only studio-recorded song from guitarist Ryo Owatari, the lyrics were also written by him. The melody of this song parallels to the melody of the song "Yesterday & Today". It was used as the drama Yome wa Mitsuboshi.'s theme song.