Squid girl

A blue-haired anime girl with a sailor hat stands on a beach, pointing excitedly, then appears distressed indoors, followed by a transformation into a dark form with red eyes and tentacles, then stands calmly with closed eyes as a red-haired girl approaches, then turns to face her with a smile, and finally is punched through a wall by the red-haired girl. The setting shifts between a sunny beach and an indoor room with a window.