After regaining her squid-like abilities, Ika Musume plans to resume her self-appointed mission to destroy all of humanity. However, her carefree job as a waitress in the Lemon beach house meant she cannot help but laze around during her spare time! On top of that, she is saddled with many problems, such as being pursued by a group of alien-obsessed individuals and catching the interest of a crazy girl. Picking up after the conclusion of the first season, Shinryaku!? Ika Musume follows the hilarious life of Ika Musume as she plots her next invasion of the surface world.

My senpai from work... is tiny and cute. Shinozaki is an office worker who is taken care of and coddled by his senior team member Shiori Katase: a gorgeous, profoundly kind, loving, and diminutive woman. Shinozaki certainly hopes that she's not doing it out of duty... but her joy of doing so increasingly exposes her feelings! (Source: MU)

Following a series of attacks that have left teachers and students alike sapped of their magic, headmistress Liza Quillyn decides to seal off the College, rendering it impossible to enter or leave the premises. As a result, Philomela Sargant is unable to comply with her grandmother Lizbeth's order to withdraw from the school. Trapped inside the College, Chise Hatori and her classmates begin to adjust to their novel and stressful circumstances. But as time goes on, Philomela's condition only gets worse—both mentally and physically. Meanwhile, details about the tragic past of Chise's roommate, Lucy Webster, continue to resurface. As Chise grapples with worries about her friends and with her evolving self, the identity of the mysterious magic-draining culprit plaguing the College may finally come to light.

Forgetful and good-natured Run Momoki has been best friends with Tooru Ichii since childhood. Despite Run being one year older, her carefree attitude and popularity with the boys is a constant headache for the overprotective Tooru. To complicate matters further, when Tooru applies to the same high school as Run, she finds out that their little circle of two has grown into a quartet. Their new acquaintances—Nagisa Tennouji and Yuuko Nishi—are classmates of Run and, in Tooru's eyes, the two must prove they are trustworthy. As a new high school year begins, the girls balance their friendship with the exhilarating opportunities of school life.