Production

After finishing with her first title in Manga Time Kirara Max (Kirari Books Meisouchuu), which was mainly about young girls dealing with moe things, Aki Hamaji considered doing a manga about bands next, as listening to bands is one of her favorite hobbies. However, she did not have any actual experience being in a band or playing an instrument prior to the making of the series, so she conducted extensive research by doing things like asking an acquaintance more familiar with the indie band scene, listening and reading more about the culture, and visiting places that are prominent to the scene (like the live house SHELTER in Shimokitazawa, which would end up being the model for the live house STARRY).

Being aware of the popularity of K-On!, also a Houbunsha-published series with a band setting, Hamaji intentionally set the story around a live house instead of mainly in school to differentiate it. She also admitted using Beck as a reference in making the series as well.

Most of the chapter covers have references to the music videos of Japanese rock bands; most of them would be songs that she liked to listen to, while some others were instead relevant to their respective chapter stories. She also avoided using onomatopoeia or creating lyrics for any of the performance scenes, leaving the finer details of the band’s performance to readers' imaginations, although some of the songs do have names originally mentioned in the manga. While the manga is mostly in a four-panel format, in serious moments she intended to have it follow a conventional manga format as well.

In an interview published shortly after the anime finished airing, Hamaji revealed that the designs of most of her characters in the series were purposely done in a simple way; commenting about Bocchi's design specifically, she said she intentionally created a character who doesn’t have any fashion sense, and her pink hair color may have been inspired by Kaoruko Moeta from Comic Girls (also a Kirara Max series), although pink-haired characters are common in Kirara titles. She also said that she decided on the color of Bocchi's guitar to be black because of how it made a good balance with the color scheme of her design, but chose a Gibson Les Paul Custom as the exact model of her first guitar because it was the first result when searching for a guitar with that specific color on the internet.[16][17] She also admitted that Bocchi's personality is a projection of hers and that she relates with Bocchi the most among all characters.Prior to the greenlighting of Bocchi the Rock!'s anime adaptation, character designer and chief animation director Kerorira was a fan of the manga for its comedy, art style, and characters, and in particular Hitori's "unhinged" nature. While meeting with animation producer Shouta Umehara at an illustrator exhibition, Kerorira brought up Bocchi in conversation and expressed a desire to work on an anime adaptation of the series. As it so happened, Aniplex had just recently proposed such a project to CloverWorks, as Umehara learned when he inquired to his superior, Yuichi Fukishima, about the possibility. Kerorira joined the project (becoming the first to do so) as its character designer after expressing his enthusiasm for the series and presenting his drawings of the characters. In addition to the character designs and animation supervision, Kerorira also contributed a significant amount of key animation to the project (estimated by Umehara to amount to somewhere between 500 and 600 cuts of animation, around two episodes' equivalent), which he stated was done in order to provide the other animators with an understanding of the "platonic ideal" of the anime's production value. Kerorira felt that providing such a baseline as the chief animation director would allow for smoother collaboration, as it would lead to a creatively unified end product while allowing the animation staff to incorporate their own individual expression, and limit the amount of corrections that would need to be made after the fact.

Series director Keiichiro Saitō, who previously served as episode director on The Idolmaster SideM and Sonny Boy, came to work on the anime adaptation of Bocchi the Rock! after Kerorira recommended him to animation producer Shouta Umehara. As Umehara was familiar with Saitō's work having served as an episode director for The Idolmaster, he considered Saitō to be an ideal choice, and Saitō joined the project as director a few days later after discussions with Umehara and Kerorira. Erika Yoshida, the screenwriter in charge of series composition, was recommended on referral from a colleague of Umehara's at Aniplex, who had previously collaborated with Yoshida on Love Me, Love Me Not. As he was aware of Bocchi's similarity in premise and genre to K-On!, Umehara spoke to Kerorira asking him what unique qualities Bocchi had which would distinguish it from K-On!, and worked to help ensure that capturing those aspects of the series was a priority of the production.

In reading the manga prior to production, Saitō was attracted to the relationships between Bocchi and the supporting cast, which were not as intimate as relationships depicted in similar works and gave Saitō the impression that "they respect each other’s individuality and personal space." He found this quality of the story to be both personally relatable and distinctive. Saitō also liked the ways in which Hitori's expressions were often exaggerated to perceptibly disturbing extents in contravention of moe conventions. This aspect of Hitori's characterization was expanded upon in the anime, as Saitō believed that "girls who are flawlessly beautiful aren’t as cute as girls who are a little mysterious or sometimes make weird faces."[18] Kerorira additionally said that Hitori's withdrawn nature made it more difficult to depict her emotions visually compared to those of the other characters. As such, her basic facial expressions were limited, while the animation relied on the more "slapstick" scenes of exaggeration to depict her emotions.[18] Although consideration was taken to ensure Hitori was consistently cute, even when the animation was exaggerating her facial features, the comedy of such exaggeration was generally prioritized.

In adapting Bocchi the Rock! from its original 4-koma format, Saitō and Yoshida introduced numerous substantial differences from the source material, such as rearranging events and altering some jokes in order to aid the anime version's pacing and surreal presentation. Saitō and Yoshida added more of a surrealist bent to the anime as they wanted to prioritize comedy and emotion over a wholly realistic depiction, and felt that the choice of cutaway gags to the anime allowed them to better convey the story while ensuring that every episode had a clear focus.[18] In integrating these cutaways into the anime, Saitō chose to contrast main character Hitori's thoughts during her instances of introspection and "strange" behavior with the external reactions to and conversations about Hitori among the supporting cast. This was done both for storytelling considerations such as the direction and pacing of certain scenes, and also to present Hitori more empathetically by showing that the supporting cast did not regard her as pathetically as she would be wont to believe. Saitō said that whether or not a conversation between the supporting cast occurring during these moments needed to be depicted in detail or not was one of the most difficult aspects of the production.

In order to create the live concert scenes of the anime, the production team recorded physical actors playing the concerts. The recording was then adapted into a computer-generated previsualization so that the animators could establish their preferred shot direction for the scenes using a virtual camera system. The previsualization was then used as the basis for the final animation. In order to ensure that the characters were portrayed accurately in these scenes, the actors were given information about the characters and advised on how to convincingly physically act as them. The music production team at Aniplex were consulted by Saitō to ensure that the ambient noise in the concert scenes was accurate to reality, although it was sometimes omitted when Saitō deemed that it would detract from an important dramatic scene.