"Monster" is a song recorded by Japanese boy band Arashi. It was released on May 19, 2010 by their record label J Storm. "Monster" is currently being used as the theme song to the drama Kaibutsu-kun (怪物くん^?, Little Monster) starring Arashi member Satoshi Ohno. It was released as a CD single in two formats: a regular edition containing two B-sides and the instrumental of all the songs, and a limited edition containing the B-side "Spiral" (スパイラル^?, "Supairaru") and a DVD.

On April 5, 2010, it was announced that Arashi would provide the theme song "Monster" for Ohno's fantasy comedy drama based on Fujiko Fujio's manga series Kaibutsu-kun. The single was released in two formats: a regular and limited edition. The regular edition included "Monster", the B-side "Spiral" and the instrumentals for both the tracks while the limited edition included the two tracks and a DVD containing the promotional video for "Monster" and its making of.

The single sold about 232,000 copies on the first day of its release on May 19, 2010, debuting at number one on the Oricon singles daily chart. On the Oricon singles weekly chart, the single placed at number one, selling about 543,000 copies. "Monster" also became Arashi's thirtieth consecutive single to rank within the Top 3 since their debut single, making Arashi the first act to achieve such a feat.

On June 24, 2010, "Monster" placed at number-one on the Oricon first half of the year singles chart by selling 654,287 copies overall. According to Oricon, "Monster" is the fourth best-selling single of 2010 in Japan.

...
Wikipedia