An Inkling girl with orange tentacles and the hero who recovered the Great Zapfish from the Octarian Army in Inkopolis Plaza. Personality: Cool and taciturn, though she was known for having a sharp tongue in the past. Gender: Female. Weapon: Hero Shot. She views Agent 4 and Agent 8 as rookies. She was once brainwashed but was rescued and freed by Agent 8.

An Inkling warrior who used Hero Weapons to dismantle the Octarian Army. Personality: Playful and easily influenced. Because she was busy with school clubs, she didn't watch much TV and didn't 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 soldier, she left the army after hearing the Squid Sisters' "Calamari Inkantation" and moved to the Inkling city. She is often called "Eight" by those around her. Personality: Airheaded, clumsy, gentle, and serious. Gender: Female. Since she is not yet fluent in the language, she speaks in broken, polite Japanese. Hairstyle: An asymmetrical bob-cut style with a long octopus tentacle fringe on the right side hanging down the side of her face.

Also known as Agent 1. She is a news anchor and one half of the popular idol duo, the Squid Sisters. Personality: Innocent, cheerful, and bright. Address term for Marie: Marie-chan. Appearance: Long twin-tails with a black-to-magenta gradient. The right tentacle is slightly longer. She wears a large white circular hair ornament resembling a calamari ring on her head. 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 hosting Splatfests at night.

Also known as Agent 2. She is a news anchor, a popular idol in the Squid Sisters, and Callie's cousin. Personality: Cool, sarcastic, and a somewhat lethargic realist. Appearance: White hair tied in a large bun on the left side, featuring lime-green ink colors reminiscent of firefly light. Speech style: A mix of Kyushu, Shizuoka, and Shikoku regional accents. Address term for Callie: Callie-chan. She is an expert sniper with a Charger. Like Callie, she isn't at the sleepover, as she's 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 Cap'n 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 of the Squid Sisters are his granddaughters. He and DJ Octavio were once comrades-in-arms, but their relationship crumbled during the Turf War, leading to his occasional kidnappings. Second person: you (archaic/polite) Personality: Caring but a bit of a show-off. Favorite food: Ohagi (sweet rice balls).

An Inkling master of machinery living on the Whirlpool Islands, a deserted island inhabited by strange, violent Salmonids. Gender: Female. Personality: Clumsy and very unaccustomed to speaking. 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. When asked about them, she describes Shiver as a woman in blue who spoke with a refined Kyoto-style grace, called herself 'Uchi,' and used a shark she called 'Master.' She describes Frye as a yellow-clad woman of the same height as Shiver, incredibly strong and energetic but a bit of a muscle-head who controlled eels. She wasn't sure if Big Man was a ray or a manta since he only said 'Ay,' but she understood him somehow and found him to be the kindest and the only male in the group.

An Inkling boy who grew close to his childhood friend Agent 4 through her teasing, eventually leading them to date. 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. Preferred weapon: Hero Shot Neo (a modified Hero Shot with a different 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 grades and trophies, while his father abused him. His mother was too paralyzed by fear to intervene. After being bullied throughout elementary and middle school, he finally ran away through a window. He was known as a runaway and was crying when Cap'n Cuttlefish found him. The Captain listened to his story and comforted him, eventually naming him Agent 6. He is slightly concerned that 6 is the 'number of the beast,' but he is intensely popular with other Inkling girls.

Originally a nameless Inkling who was a hero long before Agent 3 and the others. She inherited the title of Commander of the New Squidbeak Splatoon from Cap'n Cuttlefish. Despite her appearance, she can be clumsy and is somewhat out of shape. Personality: Taciturn, cool, and highly responsible. 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 sweet.