Maru's supernatural ability is also notable due to his surprising fighting skills which are later revealed to be connected with his origins from Heaven (The Takahara Academy) who used to experiment on teenagers.

Maru's relationship with Kiruko was inspired by buddy films and stories about siblings though Ishiguro suggested a more romantic idea since the series' beginning.

While manga artist Masakazu Ishiguro started writing Heavenly Delusion in 2018, he first revealed a teaser in late 2017 featuring the designs of Maru and fellow character, Tokio.

He rejected stories with supernatural elements and instead wanted the body swapping to be more realistic and accurate world to show what happens during a brain transplant.

He often writes metaphorical situations with Kiruko's menstrual cycle being caused by clashing with Maru's lips when awakening from a hallucination from a Hiruko's attack.

However, after reading Hirohiko Araki's comments about his character designs in the story arc JoJolion where the author decided to keep writing Jojo's Bizarre Adventure.

Another influence was the manga Akira by Katsuhiro Otomo who makes heavy emphasis on a post-apocalyptic world that Ishiguro wants to create in calm scenes involving Maru interacting with Kiruko while having meals.

[4] Writer Makoto Fukami noted the constant banters between Kiruko and Maru important for the plot setting, so they avoided trimming them in the television adaptation.

Ishiguro told him that the anime's take was identical to how he envisioned the manga and thus was glad he managed to give Maru normal conversations.

[15] Kiruko also reveals her intentions of meeting her friend Robin Inazaki in the journey which causes them to split paths once they reach his current hometown.

Shocked by his physical appearance, the doctor reveals that Maru originates from Takahara and that his parents are two former students, Tokio and Kona, and also had another child named Yamato.

This comes across as a visual resistance throughout the series against the non-consensual corruption of the children who suffer traumas while dealing with their supernatural abilities given by the doctors from the Takahara Academy.

CBR theorized Ishiguro was hiding the fact they are son and mother by tricking the viewers that both Maru's journey and the activities in Takahara occur at the same time.

[26] Clarin and Meristation compared the anime to the video game The Last of Us for the post-apocalypse setting it provides with the main duo exploring areas like its two protagonists, Ellie and Joel.

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

[30] Game Rant said that while the comedy between Maru and Kiruko always works, the sixth episode makes their sexual themes uncomfortable to the audience as during an action sequence.

The following scenes where the two start arguing about the favor were the subject of criticism by the writer especially in contrast to Tokio and Kona's relationship which is calmly handled when the two become intimate.

[31] For the series' finale, Maru's beatdown against Robin Inazaki was praised by the website for giving the audience a sense of satisfaction when the teenager nearly kills the adult as a revenge for the sexual assault on Kiruko.