Akitsu Masato, a young man, finds himself ensnared by a covert government initiative named 'Last Guardian'. His ordinary student life shatters as he learns he is destined to command the powerful robot 'Zeorymer of the Heavens'. The harsh reality hits home when Masato witnesses his supposed parents profiting from his upbringing. Last Guardian gears up for the revival of 'Hau Dragon', an ominous organization set on global domination. 15 years earlier, Hau Dragon constructed 8 formidable robots, each embodying a force of nature. Yet, their maker Kihara Masaki wrecked the robots, sparing only Zeorymer, the leader, which he entrusted to the government alongside an embryo—Masato. Now, as Hau Dragon reconstructs the remaining 7 mecha, their sights set on the 8th, Masato and Himuro must command Zeorymer in a battle against the malevolent Hau Dragon. However, both Masato and Himuro harbor hidden truths that may alter the course of this high-stakes confrontation.