The second season of Made in Abyss.
Directly after the events of Made in Abyss: Fukaki Tamashii no Reimei, the third installment of Made in Abyss covers the adventures of Reg, Riko, and Nanachi in the Sixth Layer, The Capital of the Unreturned.
Note: The last episode aired with a runtime of ~48 minutes as opposed to the standard 24 minute long episode.
— Description from AniList community (anilist.co).
