Squid Girl emerged from the deep ocean bent on conquering humanity as punishment for polluting the sea. Her invasion commenced at the beachside Lemon restaurant, where an accidental property damage forced her into working as a waitress to repay the debt. This obligation led to sustained interaction with humans. She exhibits distinct squid physiology. Prehensile blue tentacles extend from her head like hair, possessing remarkable strength, speed, and precision—capable of shattering walls or threading needles. Severed tentacles regenerate rapidly. Additional traits include emitting bioluminescent light, spewing ink from her mouth (which unexpectedly boosts plant growth and enhances food flavors), and underwater breathing. Movable fins on her head aid swimming. Critically, the white squid-shaped structure resembling a hat is an integral part of her head; its removal would be fatal. Weight-adjusting bracelets grant her the ability to lift heavy objects without losing balance. Her surface experiences gradually reshape her worldview. Initial immaturity and mischief give way to adaptability, allowing her to master complex skills like mathematics and languages quickly—she becomes fluent in English rapidly, albeit with grammatical errors. She forms strong bonds, particularly with Lemon's staff and patrons, evolving from a self-proclaimed conqueror to its protector. Her stated invasion goals persist but are often sidelined by daily distractions like movies, games, and socializing. Notable fears include natural squid predators like sharks and killer whales, inducing panic even at symbolic representations. Socially, she transitions from oceanic isolation to cherishing friendships, especially with a middle school group forming the "Invasion Club" for recreational activities. However, obsessive admirers provoke violent recoil due to her discomfort with intense affection. Her ink production yields unintended benefits, accelerating crop growth (though producing black watermelons) and improving culinary flavors. Hints of her backstory reveal a harsh underwater existence marked by food scarcity that prevented pickiness and profound loneliness, contrasting sharply with her current appreciation for companionship. Character development across her story shows increasing integration into human society. She participates in festivals, overcomes specific fears through exposure, and prioritizes defending Lemon against rival businesses. While retaining her core identity and occasional boasts about world domination, her actions increasingly focus on community protection and maintaining friendships, demonstrating a shift from hostile intent toward reluctant coexistence.