Your favourite teddy bear. That model kit that took so long to complete. The picture book you used to read over and over again. The shining stone you found that day in the park. Where do all your childhood's treasures go when you grow up? In this story, we meet fantastic creatures that gather all these little objects that fall into oblivion as they are forgotten by their owners when they step into adulthood. These creatures sneak into our world from a different dimension, and unseen by humans, they take all the ditched and forgotten "treasures" into their world. Here, they use their booty to build their own city, a fairy tale-like place called... Oblivion Island!

Recap of episodes 14-25.

Toshokan Sensou tells the story of Kasahara Iku, the first woman to join the Library Task Force. In the near future in Japan, the Media Enhancement Law has been forced upon the population censoring all books and media. To counter this, the Library Defense Force was created. To protect themselves against the Media Enhancement Law Commission, all major libraries are fully equipped with a military Task Force, who take it upon themselves to protect the books and freedom of media of the people. This anime follows Iku and her fellow soldiers as they protect various special books and artifacts from the oppression of the Media Enhancement Law Commission. A love story, war story, and comedy all rolled into one.

Kasahara Iku and Dojo Atsushi receive an emergency recall in the middle of their date as Japan is rocked by a terror attack. Their new duty is a protection detail assigned to Touma Kurato, an author. Meanwhile, the relationship between Librarians and the Media Purity Committee is also worsening.