Clāvis (Kagi)

"Clāvis (Kagi)" was written by Miyuki Nakajima and arranged by Ichizō Seo.[2] It marks Kudo's first collaboration with Nakajima in eight years, since "Setsu Getsu Ka".[3] The title "Clāvis" is latin for "key". Nakajima wrote the song with Kudo in mind. She thought a song with latin influences should be sung by someone with a strong gaze, such as Kudo.[3] Lyrically, the song deals with the theme of self-realization and explores the social nature of people. Nakajima writes about a protagonist "braving seas and people alike" in quest for the "keys of life", which she concludes is an puzzling endeavor. The song is composed in the key of C minor and set to a tempo of 100 beats per minute.[4] Kudo's vocals span one octave, from B♭₃ to B♭₄.

The latin-inspired track was praised for Kudo's ringing vocals and Nakajima's strong storytelling skills; their collaboration was deemed "miraculous".[5] Kudo was praised as a three-dimensional, versatile vocalist; the single's B-side was described by critics as equally as well-executed as the main track, in spite of being in a completely different thematic register from "Clāvis".[5]

In 2006, Nakajima recorded a cover of the song for her album, Lullaby Singer.[6]

"Clāvis" debuted at number 67 on the Oricon Singles Chart, selling 2,000 copies in its first week, and charted for three weeks.[7][8]