Yuuna, a mentally ill NEET who spends most of her time in the forums dedicated to her favorite anime Ai no Uta, stumbles across an advertisement for a desktop assistant modeled after the show's main character, Ai. She downloads it. Ai-chan turns out to be everything Yuuna ever imagined a girlfriend could be. But a relationship with no limits or friction built in is its own kind of test — and the question of whether an AI program is capable of genuine human feeling is one that neither of them is quite equipped to answer.