"Mobile Suit Gundam F90" is a manga series set in the Universal Century timeline, taking place in U.C. 0120, a decade after the events of "Char's Counterattack." The story centers on the Earth Federation Forces and their development of the F90 Gundam, a highly advanced prototype mobile suit designed to counter emerging threats. The F90 is equipped with a modular system, allowing it to adapt to various combat scenarios by swapping mission-specific equipment packs.

The narrative begins with the Earth Federation testing the F90 in space. However, the prototype is stolen by the Oldsmobile Army, a remnant faction of the Principality of Zeon, which seeks to destabilize the Federation. The Oldsmobile Army plans to use the F90's advanced technology to bolster their forces and reignite conflict. The Federation dispatches a team to recover the stolen unit, led by Ensign Daryl Marcenas, a young and inexperienced pilot who becomes the F90's primary operator.

Daryl, alongside his comrades, embarks on a mission to retrieve the F90 and prevent the Oldsmobile Army from achieving their goals. Throughout the series, Daryl faces numerous challenges, including intense battles, moral dilemmas, and the psychological toll of warfare. The F90's adaptability proves crucial in overcoming these obstacles, as it is repeatedly modified to counter the Oldsmobile Army's increasingly sophisticated mobile suits.

The Oldsmobile Army, led by Commander Annamarie Bourgain, is portrayed as a formidable adversary with a deep-seated grudge against the Federation. Their motivations stem from a desire to reclaim lost glory and avenge the fall of Zeon. The conflict escalates as both sides deploy advanced technology and strategies, culminating in a series of high-stakes battles across space colonies and asteroid bases.

Key characters include Daryl Marcenas, whose growth as a pilot and leader is central to the story; Annamarie Bourgain, whose tactical prowess and ideological convictions drive the Oldsmobile Army's actions; and various Federation officers and engineers who support Daryl's mission. The manga explores themes of technological advancement, the cyclical nature of war, and the personal struggles of those caught in its wake.

The series is notable for its focus on the F90's modular design, which introduces a variety of equipment packs such as the Assault, Long-Range, and Close-Combat types. These modifications highlight the versatility of the F90 and its role as a next-generation mobile suit. The narrative also delves into the political and military dynamics of the Universal Century, providing context for the ongoing conflict between the Federation and Zeon remnants.

"Mobile Suit Gundam F90" offers a concise yet engaging exploration of the Universal Century timeline, blending intense mecha action with character-driven storytelling. Its emphasis on technological innovation and the human cost of war aligns with the broader themes of the Gundam franchise, making it a significant entry in the series' expansive lore.