Following Madoka's rewriting of the universe, sacrificing herself and her happy normal days to save all magical girls from the cruel fate that awaited them by wiping witches out of existence, the despair still manifest into creatures known as nightmares. Magical girl Homura Akemi continues to fight alone in the hope that she will be able to see Madoka smile again.

Yuta Togashi has a problem. He used to be a "chunibyo," one of the thousands of Japanese students so desperate to stand out that they've literally convinced themselves that they have secret knowledge and hidden powers. But now that he's starting high school, he's determined to put aside his delusions and face life head on. The trouble is Rikka Takanashi, his upstairs neighbor, is just a little bit delusional herself. And she knows all about his past indiscretions.

本作主人公冈部伦太郎（宫野真守 配音）是个患有严重中二病的大学生，自称为“凤凰院凶真”的他和伙伴们组成了“未来发明研究所”，在位于秋叶原的一个简陋实验室内进行各种古怪发明和调查。
2010年7月28日这天，冈部和青梅竹马真由理（花泽香菜 配音）一同去了科学讲义会场，在那里，他们遇见了天才少女牧濑红莉栖（今井麻美 配音）。让人意想不到的事情发生了，冈部在会馆楼道内听到一声惨叫，他闻声而至，发现了倒在血泊中的牧濑。冈部用手机短信将这件事告诉好友桥田至，这个举动，让世界都颠覆了。实验室里那个所谓的“未来道具”，竟然真的可以左右世界的进程，冈部自此成了孤独的观测者。
这一切都是命运石之门的选择。