Ink Theory

"This classically trained, all-female 6-piece band creates jazz and samba-inspired battle music. They owe their unique sound to a blend of academic music theory and modern sensibilities. Ink Theory's eclectic approach makes them quite popular with young Inklings and middle-aged Inklings alike."

- Live from the Squid Research Lab

Ink Theory is an all-female six-piece jazz band. The band has a history of classical training, with the members learning music since their childhood long before making their debut. Their songs were added in Version of.

Yōko (ヨーコ)
The band's trumpet player, and frontwoman, though she sometimes feels overshadowed by the other members' personalities. She is an Inkling with a mutation that allows her tentacles to have multiple colors, but it rarely proves useful. She is described as often getting nervous before large productions. She also has a weakness to atmospheric pressure; on rainy days she is said to have a dead face and while she struggles in sunny weather as well, she is a hard worker and always gives a solid performance. She has a sister in high school.

Karen (カレン)
The band's pianist is a nautilus who graduated at the top of her class from a famous musical university. She has participated in overseas competitions and has won many awards, as well as offering emotional support to the band. She provides the band with a crisp atmosphere, and looks self-assured, though she worries that she is not loved by fans. She formed Ink Theory after being amazed by Hightide Era's music.

Bibi (ビビ)
The kazoo player is an Inkling who graduated from a famous music academy. She is closer to the public than the other members of the band, and is renowned for her beauty, often being considered the "flower" of the band. As a result of this, she gets a lot of attention, often being pulled in front of cameras. Fans address her with the Japanese honorific "-sama", which is used to address those one considers to be on a higher rank than oneself. She is a large spender but has never struggled much financially.

Aachin (あーちん)
The band's bassist is a sea urchin, specifically Hemicentrotus pulcherrimus. She grew up in a strict household with parents who are famous musicians. For a short while, she favored bands with a different musical style from her parents, but lately, she has been observing classical music in a new light. She is romantically inexperienced, often falling for self-degrading people.

Mayaya (マヤヤ)
The band's percussionist. She is a sea anemone who joined Ink Theory after graduating from a music academy. While her professor recommended she become a music instructor herself, she decided she would rather get experience creating her own music, first. She mainly plays with Ink Theory, but occasionally freelances percussion for other bands.

Kitamura (きたむら)
She is a sea urchin and the band's drummer. She acts as the band's mascot. She has a high singing voice and regularly follows new fads. She lives alone, but keeps close attention to her curfew.

Trivia

 * According to a anniversary Famitsu interview with the developers, in-universe, Ink Theory was inspired by Hightide Era. This connection can be seen in the outfits worn by both bands: Hightide Era wears mainly black with red neckties, and Ink Theory wears mainly black with gold ties.
 * Like MURASAKI of Squid Squad and unlike in-game sea urchins Spyke and Murch, Kitamura's face does not appear to be distinguished from the spiny part of her head.
 * Ink Theory is the largest band in the Splatoon series, with six members.
 * Strangely, in the Valentine's Day artwork, Yōko's hat appears to have actual Japanese kanji, rather than wording in the Inkling language. Specifically, it reads "可憐," which translates to "pretty", while coincidentally also being pronounced "Karen".
 * An urchin wearing a bow resembling Kitamura can be seen in the crowd of Pearl's gig in the photo in Marina's chat room. Whether this is Kitamura or a similar-looking character is unknown.
 * In-universe, they have a rivalry with the Bottom Feeders, since both bands debuted simultaneously and utilize classical instruments, but have conflicting styles.

Etymology

 * Aachin's name is a reference to "urchin", the species which she is.
 * Ink Theory's name seems to come from Jazz Theory or Music Theory.
 * Bibi is nicknamed "Queen Bibi", which seems to be a reference to Beyonce's nickname "Queen B".
 * Ink Theory's name on the album art has what looks like a bass clef in the left, connected 8th notes in the middle, and a piano dynamic in the end.