Hei no Naka no Biyōshitsu (塀の中の美容室, "Beauty Salon in Prison"), also known as The Depth of the Sky, is a Japanese manga series written by Mina Sakurai and illustrated by Marco Kohinata.

Hei no Naka no Biyōshitsu is Mina Sakurai [ja] and illustrated by Marco Kohinata.

[1] The series ran in Shogakukan's seinen manga magazine Big Comic from March 25 to May 9, 2020.

[2][3] Shogakukan collected its five chapters in a single tankōbon volume, released on August 28, 2020.

[4][5] Hei no Naka no Biyōshitsu received an Excellence Award at the 24th Japan Media Arts Festival in 2021.