Ika Musume (referred to as Squid Girl in the English dub) is a girl who comes from the sea with plans to invade humanity as punishment for the pollution done to the sea. However, after causing damage to a beach house, she is forced to work as a waitress to pay for the damages and also sleeps at the Aizawa residence. Her name, イカ娘 Ika Musume literally means "Squid Girl". Ika Musume is voiced by Hisako Kanemoto
Like a squid, she has ten fully controllable tentacles that protrude from the top of her head like hair. These tentacles are very strong, incredibly dexterous and she can control them effortlessly; they also can stretch to a huge range, and they have a variety of offensive capabilities. The squid ink she can spew from her mouth tastes delicious and is used for the 'squid ink spaghetti' dish in the Lemon Beach House. She enjoys shrimp very much; in fact, it is her favorite food. She greatly fears natural predators like killer whales, to the point that even swimming floats shaped like killer whales terrify her. Like some species of squid, she possessed bioluminescence.
She has a "hat" resembling the head of a squid, which is, above all else, how she recognizes her own kind. If someone makes a fake, she will instantly believe that they are one of her own species, and without it, she will not even recognize a fake version of her own head. While it is called a hat, it is part of her body, which allows her to control the fins. She didn't know that she could do that, so they serve no apparent purpose. She later uses them to slap people like Sanae. According to her, she will die if she takes it off, and trying to do so casually reveals that it is directly attached to her head. When trying to forcibly remove it, it starts to make a ripping sound from the strain, gives her enough pain and shock to recover from amnesia and leak squid ink from the tear.
Due to her small stature, she can adjust her weight in order to pick up larger objects without being toppled over. Adjusting the bands on her wrists allows her to go from anywhere between 0.0005kg to 20,000kg in an instant. She can float on an updraft at her lightest, allowing her to take "flight."
Due to the dexterity and the ability to manipulate her tentacles at will, she can use her tentacles for many purposes. She can deliver a powerful smack, wrap them around a foe and hoist them into the air, or coerce them through tickling She can use her tentacles to carry many plates at once while working at the beach house. Drawing with her tentacles results in hyper-detailed masterpieces. She highly excels at physical activities such as volleyball and drumming. Despite her usual naivety, she also displays a high level of intelligence occasionally—it is revealed she is a mathematical genius, capable of working with such functions as the Fourier analysis and the Poisson summation formula. Chizuru also notes how quickly she learned how to speak Japanese and interact with humans.
Level of intimacy based on how one addresses Ika:
|イカ 娘ちゃん||Ika Musume-chan||Chizuru Aizawa||Though she wants to be closer to Ika, Ika is wary of her|
|イカ 娘||Ika Musume||Eiko Aizawa, Gorō Arashiyama||No nonsense, fights frequently|
|イカ 姉ちゃん||Ika Nee-chan||Takeru Aizawa, most kids||Respects Ika as an elder|
|イカ ちゃん||Ika-chan||Sanae Nagatsuki, Kiyomi Sakura||Loves Ika|
|イカ 先輩||Ika senpai||Yuka Nishimura, Tomomi Mochizuki||Loves Ika|
|イカ の嬢ちゃん||Ika no Jō-chan (miss)||Gorō's mother||Motherly figure, feeds Ika until she becomes fat|
|イカ さん||Ika-san||Ayumi Tokita||Respects Ika|
|イカ 星人||Ika Seijin (alien)||Cindy Campbell||Tries to capture Ika and bring her to her labratory|
|イカ の人||Ika no hito (person)||Nagisa Saitō||Considers Ika as a treat to humankind|
|イカ 女||Ika onna (woman)||Aiko Saitō||Considers Ika as a rival|
- Chizuru Aizawa: Although she likes to tease Ika, she wishes to be closer to Ika, just as Eiko and Takeru do. The main obstacle to her wish is Ika's wariness to her in general and to her eyes in particular. During Kiyomi's visit, Chizuru open her eyes to convey support, but Ika interprets it as silent treat. When Chizuru wears contact lenses, accidental eye contacts causes Ika to squirt a slice of lemon to Chizuru's eyes - to force them close.
- Eiko Aizawa: Although Kiyomi Sakura is Ika's first friend by choice, Eiko is her first and best friend on the surface world. Apart from sharing the same room and working together at Lemon, they hang out together outside.
- Her dress is not an ordinary one, with at least 2 known features: