The MSN-06S Sinanju, known simply as Sinanju, makes its prominent appearance in the Mobile Suit Gundam Unicorn novel, its OVA adaptation, and the television re-cut. Piloted by Full Frontal, it is a modified iteration of the MSN-06S Sinanju Stein, originally developed by Anaheim Electronics for the Earth Federation's "UC Project." The mobile suit's movable frame incorporates Psycho-Frame materials, a technological innovation in its design.

Originally crafted as the Sinanju Stein, this prototype was stolen and adapted into the MSN-06S Sinanju by "The Sleeves," a Neo Zeon remnant group led by Full Frontal. The Sinanju undergoes significant aesthetic and functional modifications, with all Gundam-like features (excluding head-mounted vulcan guns) replaced with distinctive Zeonic design elements and weaponry. Painted in striking crimson with intricate gold engravings, the Sinanju becomes a symbol of the Neo Zeon forces.

The unique decoration not only reinforces the mobile suit's armor but also serves as a symbolic design to command the Neo Zeon remnants. To address concerns about the armor's elasticity, enhancements are made to increase the pilot's survivability. The beam coating transitions from the conventional two-layer structure to an advanced five-layer structure, and the entire cockpit block is shielded with Luna Titanium X material, fortifying the Sinanju's armor as a flagship machine.

In addition to its formidable armor, the Sinanju boasts thrust deflector thrusters resembling the wings of a bird of prey, along with flexible thrusters on both legs and shins. Combined with numerous thrusters distributed across its body, the mobile suit exhibits acrobatic maneuvering capabilities beyond the reach of standard MS units. With its crimson exterior, overwhelming combat prowess, and mono-eye sensor, the Sinanju encapsulates the essence of the legendary "Red Comet" for all who encounter it.