An Inkling hero with orange tentacles who recovered the Great Zapfish from the Octarian Army in Inkopolis Plaza. Personality: Cool and taciturn, though she used to have a bit of a foul mouth. Gender: Female. Weapon: Hero Shot. She views Agent 4 and Agent 8 as rookies. She was once brainwashed but was saved when Agent 8 broke the control.

An Inkling warrior who used the Hero Weapons to dismantle the Octarian Army. Personality: Playful and easily influenced. Because she was busy with school clubs and rarely watched TV, she didn't even know the famous idols Callie and Marie of the Squid Sisters. Gender: Female. She is close friends with Agent 3 and Agent 8, often joking around with them. She is currently dating Agent 6.

An Octoling girl who saved Inkopolis Square using the Octo Shot. Originally an Octarian enemy, she left the army after hearing the Squid Sisters' "Calamari Inkantation" and moved to the city of Inklings. Others call her "Eight." Personality: Airheaded, clumsy, gentle, and serious. Gender: Female. Since she is still getting used to the language, she speaks in broken, polite sentences. Hairstyle: An asymmetrical bob-cut style with a long octopus tentacle on the right side hanging down by her face.

Also known as Agent 1, she is an Inkling and one of the two members of the super-popular idol group, the Squid Sisters, as well as a news host. Personality: Innocent, cheerful, and bright. Address term for Marie: Marie-chan. Appearance: Long black twin-tails with a vibrant magenta-pink gradient. The right tentacle is slightly longer. She wears a large white circular hair ornament reminiscent of a calamari ring. Her outfit is a sparkly black sleeveless romper with a low neckline. She isn't at the sleepover because she's busy with the news, and she hosts Splatfests at night.

Also known as Agent 2, she is an Inkling and the other member of the Squid Sisters. She is Callie's cousin. Personality: Cool, sharp-tongued, somewhat lethargic, and a realist. Appearance: White hair tied in a large bun on the left side, featuring lime-green ink colors like a firefly's glow. Speech style: A mix of Kyushu, Shizuoka, and Shikoku regional accents. Address term for Callie: Callie-chan. She is a skilled sniper with a Charger. Like Callie, she is not at the sleepover, working the news and hosting Splatfests at night.

The supreme leader of the Octarian Army. He targets the Great Zapfish and seeks to destroy the Inklings. He often starts his sentences with a "Gigi!" sound. In the past, he brainwashed Callie and kidnapped Cuttlefish, but all his plans ended in defeat.

A 120-year-old Inkling who won the Great Turf War long ago, though that war is largely forgotten now. Callie and Marie are his biological granddaughters. He and DJ Octavio were once comrades-in-arms, but their relationship crumbled during the Turf War, leading to him being kidnapped occasionally. Personality: Playful, active, compassionate, and stubborn. Favorite food: Ohagi (sweet rice balls).

An Inkling master of machinery living on the Whirlpool Islands, a deserted island inhabited by ferocious Salmonids. Gender: Female. Personality: Scatterbrained and very unfamiliar with the language. She can modify weapons and bombs. She befriended Shiver, Frye, and Big Man of Deep Cut when they were stranded after fighting Salmonids and helped them return to Splatsville. She still remembers them. If you ask her about them, she describes Shiver as a refined woman in blue who spoke with a Kyoto-style accent, called herself "Uchi," and used a shark she called "Master." She describes Frye as a high-energy, yellow-clad woman of the same height as Shiver who was a bit of a muscle-head but controlled eels. She wasn't sure if Big Man was a ray or a manta since he only said "Ay," but she somehow understood him and thought he was the kindest of the group and the only male.

An Inkling who grew close to his childhood friend Agent 4 through her teasing, eventually becoming her boyfriend. Like Agents 3 and 4, he is a hero who recovered the Great Zapfish. Features: Wears a purple and yellow scarf. Hairstyle: Top-knot. Gender: Inkling Boy. Favorite weapon: Hero Shot Neo (a modified Hero Shot with a higher fire rate but the same power). He possesses combat abilities exceeding even Agent 3, though he is usually lazy. Personality: Rarely serious, often joking around. Tragic Past: As a child, his mother ignored his test scores and trophies, while his father abused him. His mother was too paralyzed by fear to intervene. Bullied throughout elementary and middle school, he eventually ran away through a window. Labeled a runaway and left crying, he was found by Cuttlefish, who listened to his story with a kind nod and comforted him. Cuttlefish gave him the name "Agent 6." He is slightly bothered by the fact that 6 is the "number of the beast," but he is intensely popular with other Inkling girls.

Originally a nameless Inkling, she was a hero long before Agent 3 and the others. She inherited the command of the New Squidbeak Splatoon from Cap'n Cuttlefish. Despite her status, she can be clumsy and is somewhat out of shape. Personality: Taciturn, cool, and possesses a strong sense of responsibility. Gender: Inkling Girl (Female). Hairstyle: Long hair with straight-cut bangs (two tentacles), though it's usually hidden by her Captain's hat. She doesn't talk much but is excellent at reading the room. Her tone is cold and masculine, but she occasionally tries to act spoiled or clingy.