Kazuya Kinoshita is a 20-year-old college student who has a wonderful girlfriend: the bright and sunny Mami Nanami. But suddenly, he doesn't. Without warning, Mami breaks up with him, leaving him utterly heartbroken and lonely. Seeking to soothe the pain, he hires a rental girlfriend through an online app. His partner is Chizuru Mizuhara, who through her unparalleled beauty and cute demeanor, manages to gain Kazuya's affection. But after reading similar experiences other customers had had with Chizuru, Kazuya believes her warm smile and caring personality were all just an act to toy with his heart, and he rates her poorly. Aggravated, Chizuru lambastes him for his shameless hypocrisy, revealing her true pert and hot-tempered self. This one-sided exchange is cut short, however, when Kazuya finds out that his grandmother has collapsed. They dash toward the hospital and find Kazuya's grandmother already in good condition. Baffled by Chizuru's presence, she asks who this girl might be. On impulse, Kazuya promptly declares that they are lovers, forcing Chizuru to play the part. But with Kazuya still hung up on his previous relationship with Mami, how long can this difficult client and reluctant rental girlfriend keep up their act? [Written by MAL Rewrite]

The Daihasei Festival has begun, and that of course means that Tokiwadai Middle School—a prestigious all-girls' middle school—is competing too. Despite the participation of the "Ace of Tokiwadai," Mikoto Misaka, the other students who are participating are still putting their utmost effort into winning, no matter how impossible the feat may seem against her might. However, not all is fun and games. Due to the the festival, Academy City opens to the outside world, and various factions have begun plotting ways to infiltrate the city. Misaka appears to be on their radar, and as the festival proceeds, people lurking from the shadows begin to emerge... Toaru Kagaku no Railgun T brings back the Tokiwadai Ace and her friends as they dive deeper into the dark side of Academy City. From terrorist attacks to ruthless underground projects, anything is possible in this city. [Written by MAL Rewrite]

This two-part OVA is a series of shorts in relation to the School Rumble series. This OVA fills in gaps with new content between episodes from beginning to nearly the end. (Source: ANN)

A short 2 episodes attempt to conclude the series. Karasuma goes to America after the end of the third term. Will Harima finally confess? What will happen with Tenma and Karasuma?