The Makai fight a secret war against the demon forces known as Horrors, evil creatures that manifest themselves through darkness to devour Humanity. On the frontlines are the Makai Knights, given the task of watching over a district and eliminating any Horrors that manifest there. GARO follows the tales of the Knights bearing the title of ‘Golden Knight Garo’, and their duty to vanquish the Horrors and protect Humanity from the darkness.

The TLT is a covert international anti-monster unit established secretly to combat Space Beasts, mysterious monsters that are out to attack humans in the year 2009. One of the TLT's new recruits, Kazuki Komon, is attacked by one of them prior to reporting for duty. However, he is saved by a silver giant that he names "Ultraman". What no one knows is that the silver giant is an Ultraman — to be precise, Ultraman Nexus, ready to fight the Space Beasts to save the planet Earth.

Shiori, who was called out by her friend Akiko after a long time, was told that she was going to get married. Although Shiori congratulated them with a smile, Akiko's boyfriend Takatsuki was a man who had secretly had feelings for her even before she became a NR. Meanwhile, mysterious disappearances were occurring in the town...