Reason (stylized as REASOИ) is the twelfth extended play by the South Korean boy group Monsta X.

[7][8] "Beautiful Liar" is a rhythmical and powerful punk rock-style song that sings the reason for love found in the most extreme and dangerous relationship.

It has highly addictive beat and high-quality vocals and performance, providing a more intense sense of immersion.

[9] "Daydream" is a song that showed the group's soft and alluring side, while "Crescendo" creates a strange charm with the sound of a mixture of the Korean traditional musical instrument geomungo and taepyeongso.

[12] Their comeback showcase was held to commemorate the release of their album, as well as to showcase the stage of its b-side songs, through Naver Now on January 10,[13] as well as the global K-pop rhythm game SuperStar Starship's commemorative mini-album Reason new song update release, which contains a special design with a deadly concept.

[18] Abbie Aitken of Clash described it as "an accumulation of Monsta X's past eight years", with six contrasting and neatly polished tracks, each showcasing "a different genre highlighting the group's versatility".