[1] "Clāvis (Kagi)" was written by Miyuki Nakajima and arranged by Ichizō Seo.

[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 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 just as well-executed as the main track, in spite of being in a completely different thematic register from "Clāvis".