Mori and his colleagues worked to properly convey the setting seen in the manga, while balancing the screen time between Maru and Kiruko, and the students from Heaven.

Fukami avoided trimming the constant banter between Kiruko and Maru, which they noted was important for the plot setting.

[5] Mori said because the episodes were 20 minutes long, they had to decide how much screentime to give each side of the narrative to properly show the characters' stories.

[6] Maru's action sequences were animated by Tetsuya Takeuchi, who wishes to match wuxia-like choreography with active camerawork.

Because manga is drawn black and white, Mori was conscious of adding color to the world, such as the ruined landscape and the school, to make it look more attractive.

The director thought Maru meets Kiruko from a place where he does not know his own past, and gradually gains an ego.

[4] According to Mori, the original work already contains the message Ishiguro wanted to convey so the production side does not add anything else but has many elements, such as disasters and technology.

[8] Regarding the anime adaptation, the director and production team had to think about the overall structure so Ishiguro had to tell them the manga's full story.

[9] Both Satō and Sayaka Senbongi initially had problems understanding their characters Maru and Kiruko, respectively, because there was little information about their pasts in the first episodes.

[11][12] It was directed by Hirotaka Mori, with scripts written by Makoto Fukami, character designs handled by Utsushita of Minakata Laboratory, and music composed by Kensuke Ushio.

[20] They noted the series appears to heavily focus on gender, not on Kiruko's themes that come across as negative as the reviewer still found the character interesting based on how they are written.

[21] The reviewer praised the relationship between Maru and Kiruko for the way they care for each other, and noted the flashback's incestuous "angle might just be sensationalism for the sake of it, but I don't mind that extra splash of taboo when the full picture is this interesting".

Prickett was troubled by the repercussions of this twist on Kiruko's feelings because her early scenes in the first episode now made her look incestuous.

[26] Clarín and Meristation compared the anime to the video game The Last of Us for its post-apocalypse setting with the main duo exploring areas like The Last of Us's protagonists Ellie and Joel.

[27][28] NME enjoyed the mystery and lack of exposition dumps, positively comparing the premise to those of The Leftovers and Station Eleven.

[30] The Philippine Star praised the series for focusing on gender dysphoria through the relationship between Maru and Kiruko without queerbaiting audiences in a manner similar to "switcheroos" like Ranma ½ and Sailor Moon.

[8] Ishiguro praised Senbongi's work in the fifth episode when delivering Kiruko's mental breakdown, having edited he script to add new lines to the anime.