Acht

"Everyone, meet Dedf1sh. Previously a promising, up and coming DJ, her pursuit of breakbeat perfection eventually led her to a subterranean test facility, where she was "sanitized." Though little of her former self remains, she continues crafting DJ delicacies, and the halls of the test facility echo with her bumping tracks to this very day."

- Live from the Squid Research Lab

Ahato Mizuta (ミズタ アハト Mizuta Ahato), better known by her psuedonym Dedf1sh, is a musician in Splatoon 2 whose songs were released as part of the Octo Expansion. Once a normal Octoling, she entered the underground test facility and became sanitized, losing her free will.

Songs
Before the release of the Octo Expansion, a video entitled 'Catalog Mix' featuring short sections of some of the songs was made available. It includes several songs heard in the Octo Expansion and its missions. The only song that was named prior to Octotune's release was Splattack! (Octo).

Description
Before her disappearance, Dedf1sh was a promising DJ who spent most of her days making and mixing songs. She had learned every genre of music, causing her music to be described as "mimetic". She is diligent and hardworking, but it's said that she had "doubts and conflicts about production" and let herself be sanitized to devote herself to nothing but music. Due to her sanitization, she doesn't make music considering others, instead letting what comes out of her "inner self" take form.

Trivia

 * In her album art, Dedf1sh uses a series of turntables each with the number 8 on them and eight buttons, corresponding to an octopus' number of arms and the overall recurring number eight through the Octo Expansion.
 * The background of the album art features the Kamabo Corporation logo, also seen in places such as the CQ card and C.Q. Cumber's hat.
 * Oddly, her numbered catalog of songs appears to be missing select numbers: 3, 7, 10, 15, 17, and 18.
 * When adding the numbers from the title of each song and then dividing the total by the number of songs Dedf1sh has composed (in other words, taking the average of the remaining numbers plus an extra 0 to represent Splattack! (Octo)), the result is eight, the recurring theme of the Octo Expansion.
 * The music made by her wasn't planned to have a musician attached to them, due to being intended to nothing but background music and not have any sort of backstory. After Seita Inoue ended up liking the music a lot, he created Dedf1sh to bring more attention to it.
 * Paul of SashiMori bears some resemblance to her, with both having the same skull or octopus icon on their headwear and wearing black tops. Whether or not this means anything is unknown.
 * In Splatoon 3, Dedf1sh’s signature can be found on the exterior of Hotlantis.

Etymology
Dedf1sh is a portmanteau of "dead" and "fish", in reference to her sanitization and no longer showing vital signs. The name is likely mimicry of the DJ and musician, deadmau5. Both are stylized in leetspeak, which is a nod to computer hacking evidenced by the purposeful misspelling of "dead" and her song titles.

"Mizuta" likely refers to the Giant Pacific octopus, or "mizudako" in Japanese, while "Ahato" is the Japanese rendering of "Acht", or German for "eight".