At the end of the 21st century, the discovery of a new energy source called "DG energy" (short for "divine grace energy") has revolutionized Earth's economy and allowed humanity to colonize space. However, when the initial expedition reaches Pluto, they are attacked by a mysterious, giant life-form known as "Nergal."
 
The Earth Alliance Army fights back by creating an "AG Unit" using ancient robot weapons known as the "G's Frame" which were excavated from archaeological sites all around the world. Girls with special qualities known as "Ancient Girls" can pilot these robots against the Nergal. However, the first AG Unit suffers heavy casualties in the Jupiter Trojan campaign, and the pilot of Unit 04, Minamiya Reiu, goes missing-in-action...
 
Years later, Minamiya Reika, the younger sister of Reiu, enlists with the AG Unit to search for her sister and to protect the Earth from the Nergal. A story of friendship, ancient robot weapons, and battles to the death with the Nergal ensues.
 
(Source: Crunchyroll News)

Episode 1 - G's Frame

Episode 2 - Army of Ancient Girls

Episode 3 - Toward the Universe

Episode 4 - The Gravestone on the Moon

Episode 5 - Rebellion

Episode 6 - Relics on Mars

Episode 7 - The Universe in Dream

Episode 8 - Gandharva in the Deep Ocean

Episode 9 - Heralds from the Extra Dimension

Episode 10 - Battles in the Mega Red Spotted Area

Episode 11 - The Giant's Resurrection

Episode 12 - Human's Decision

Seven Stone Entertainment

bilibili

Youku

Ancient Girl’s Frame