The anime was a joint production between CloverWorks (Rascal Does Not Dream of Bunny Girl Senpai (2018), Darling in the Franxx (2018)) & Wit Studio (Attack on Titan (2013) (seasons 1-3), Vinland Saga (2019).)
The character design for Anya bares a striking resemblance to the main character of manga writer Tatsuya Endo's previous work, a One-Shot called, "Rengoku no Ashe." Both characters have pink hair and wear similar hair accessories, although Ashe is older and has a more hardened personality.
In Ep. 23, Loid suggests giving some Priceless Diamond Rings that Nightfall inadvertently stole to the Handler as a Gift. Sure enough, at the end of the Episode, the Handler can be seen wearing the Rings on her Hand.
Actress Bryn Appril has appeared as a Temporary Replacement as both Nightfall & Anya in Different points of the Series. Appril also took over for Anya's Megan Shipman's role on Girlfriend, Girlfriend during the same Time due to Shipman being on Maternity Leave.
Based on a spy action comedy manga by Endou Tatsuya Serialized in Shounen Jump+.