For too long, humans have been polluting the ocean, wreaking havoc on the marine life. In response, a determined squid named Ika Musume emerges with a mission to avenge her underwater comrades. Armed with formidable squid-like powers, including hair-tentacles and ink-spitting abilities, she sets out to punish humanity for their reckless deeds. However, her plans take an unexpected turn when she challenges the Aizawa sisters at Lemon Beach House, only to face a humbling defeat. To repay the damage she caused, Ika Musume reluctantly becomes a waitress at the beach house. Despite her initial goal of world domination fading, she finds a sense of belonging and joy in her new role. Follow the whimsical journey of Ika Musume in Shinryaku! Ika Musume as she navigates her quirky life on land, forging friendships and creating unforgettable moments with her unique charm and squid ink dishes.