Sentai Filmworks announced on Thursday that its home video release for No. 6 is going out of print. Sentai Filmworks confirmed with ANN that its license has expired.

Sentai Filmworks licensed the anime in 2011 and released it on Blu-ray Disc and DVD in 2012. The Blu-ray Disc release is still available on sale on Sentai's store for US$9.99.

The anime adaption of Atsuko Asano's novels aired in 2011, and Crunchyroll streamed the series as a simulcast. The show is still available for streaming on Crunchyroll from publisher Aniplex of America.

Source: Email correspondence