Ultraman F (ウルトラマンF Urutoraman Efu) is the titular character of her own novel Ultraman F. She was born when Giant Soldier F (an alternate Akiko Fuji) was irradiated from the beam attacks of Dark Faust, Mephisto and Zagi.
While fighting alternate versions of Dark Faust, Dark Mephisto, and Dark Zagi, all three dark giants open fire their finishers on Giant Soldier F. During that time, the combined beam caused the Balloonga cells of Ultra Armor F and the Mefilas Bot to react and transform her into a literal Ultra Warrior. With her newfound power, Ultraman F proceed to overpower both Faust and Mephisto before she engaged in a teleportation chase across different regions on Earth and sealed his fate on the moon. Mephisto survived the conflict and moved on by the words of his lover.
F would face against the invasion of Yapool (as U-Killersaurus Neo) on Nagoya, Japan, briefly held hostage before she escaped and destroyed them. Her final battle would be against a Hyper Zetton summoned by Inpei Seant to enact his revenge. Hyper Zetton proved itself as a formidable opponent to F until it smashed her Timer, causing F to exert her full strength and finally destroying the monster. With F can no longer return to normal, Ide once more provide a solution by creating a virus through her twin sister's DNA.
Fuji lost her powers as Ultraman F due to the deactivation of Mefilas Bots but swears that one day her alter ego shall return.
- Height: Unknown
- Weight: Unknown
- Age: 22 years old
- Home World: Earth
- Weakness: There is a Color Timer on her chest that operates on the 3 minute rule, but instead of measuring her energy, it served as the timer noting the time limit before Fuji can no longer be forcefully return to normal via the Thermal Atomic X-ray. If the Timer is destroyed or Fuji cannot revert to human form, crystal shards would emerge from F's body in a similar vein to Ultraman Saga.
- Mefilas Bot (メフィラスボット Mefirasu Botto): Nanobots contained within Fuji's body, they were responsible for her transformation into Giant Fuji during her kidnapping by Alien Mefilas. According to Ide, the nanobots are bounded to her DNA and the estimated number are 80 x 1016. The 'Pattern Ultra' emitted by Hayata can reactivate the nanobots, though this time Fuji is in control.
- Healing Factor: The Mefilas Bots are capable of healing Fuji's injuries at a faster rate. In addition, when being exposed with Thermal Atomic X-Ray, the Mefilas Bots are able to negate said radiation's side effect (Cancer).
- Pattern Ultra (パターン・ウルトラ Patān Urutora): The life energy of an Ultraman emitted by Ultraman F. Former Ultraman host Hayata also possessed remnants of this energy, which was responsible for reactivating Fuji's Mefilas Bot once more.
- Balloonga Aegis (バルンガイージス Barunga Ījisu): Since the transformation into Ultraman F costed Balloonga's energy absorption, Ide created an armor for F to use, which absorb incoming energy beams. But since the Ultra cannot exploit the absorbed energies, said armor was destroyed by Imago Hyper Zetton's Dark Fireball.
- Ultra Armor F's abilities: Since Ultraman F's skin is developed from Giant Soldier F's armor, she still retain these abilities:
- Zero Gravity Bullet (無重力弾 Mujūryoku-dan): The same bullet that SSSP used to defeat Zetton once.
- Barrier Generation: F can create a protective barrier.
- Dark Zagi's data: Since Zagi was also one of the driving factors of F's birth, she gains the information and combat strength of Dark Zagi, allowing Fuji/F to turn the tables against the giant of darkness.
- Teleportation: Ultraman F is capable of teleporting towards various continents on the Earth, as well as to the Moon. This was made to counter Zagi's attack and is enhanced when F received "crystallization".
- Zagi Galaxy (ザギ・ギャラクシー Zagi Gyarakushī): To counter Zagi, F can also summon meteorites from asteroid belt.
- Ultra Powers: As an Ultra, Fuji can shape her energy beams through her own mind. Some are homages to the original Ultraman while others are tributes to past Ultraman.
- Spacium Beam (スペシウム光線 Supeshiumu Kōsen): Based on Ultraman's "+" style finisher.
- Dismembering Halo (八つ裂き光輪 Yatsuzaki Kōrin): Based on Ultraman's Ultra-Slash.
- An 870,000 degree energy beam fired in a similar pose to Ultraman's Ultra-Attack Ray. According to novel, Fuji created this from Zagi's memories of fighting a certain Ultra Warrior.
- Unnamed L-style Beam: Created in a similar pose to Ultraman Ginga's Ginga Cross Shoot.
- Energy Body Charge: Based on Ultraman Mebius Infinity's Cosmo Miracle Attack.
- Energy Punch Attack: Based on Ultraman Saga's Saga Maximum.
- As Giant Soldier and Ultraman, the letter "F" in her notation means "female" and "Fuji".
- This is also makes sense since she is the female and coincidentally the "final" project of Giant Soldier program. The Ultraman notation is due to neither of the characters having heard of a female Ultra Warrior (Ultrawoman) before.