The protagonist and a boy who holds the key to the mystery surrounding the giant humanoid weapon, "Didarion", which was discovered aboard an extaterrestial battleship called the Eltsard in the Antarctic ice cap.
- Amnesiac Hero: About all he remembers is his name and his mission to protect humans.
- Ineffectual Loner: Dido distances himself from others; about the only person he opens up to is Meguru.
- Mystical White Hair: Has a full head of white hair and the ability to transform into Didarion.
The heroine who serves as the Didarion's observer, Meguru is the daughter to Professor Daimon, head of "MART", and is a "Phenomena", individuals who use special neural abilities called "Third Man Phenomenon". She pilots the "Merafdin", another Humongous Mecha discovered on the Eltsard.
- The Leader: She serves as this for MART's test pilots.
- Only I Can Make It Go: The Merafdin can only be used by Phenomena like Meguru due to its user interface taking advantage of the Third Man Phenomenon.
- Rose-Haired Sweetie: She has pink hair, and is the only member of her team that treats the Didarion as more than a machine, trying her best to communicate with it.
The sub-heroine and Meguru's co-worker, Yunna originally volunteered to join the air force, training to become a fighter pilot, but was drafted into MART when her abilities as a Phenomena were discovered. She pilots a Grafdin, a "Dominant Trooper" developed by MART using data from the Merafdin that harnesses Third Man Phenomenon.
- Ace Custom: Her Grafdin has a mostly reddish color, with light brown highlights.
- Aloof Dark-Haired Girl: Has short, black hair, and is reserved almost to the point of being cold.
A Phenomena test pilot for MART who previously worked in human resources for one of their Japanese partner companies, Sakimi has a mild and serious personality, but with a strong sense of curiosity.
- Ace Custom: Her Grafdin is blue with light brown highlights.
- Token Wholesome: She's the only member of the Grafdin pilots whose outfit exposes no skin below her neck, giving her a prim and proper appearance.
A test pilot for MART, Linaria was previously a MART engineer until she was drafted to use a Grafdin upon discovering she was a Phenomena.
- Ace Custom: Her Grafdin is a mostly bluish color, with purple highlights. The sensors located in the head are also stronger than other Grafdins.
- Big Beautiful Woman: Linaria is considerably bigger and chubbier than other original characters seen in Super Robot Wars, but that doesn't stop her from being attractive.
- The Quiet One: She doesn't talk much, and whatever she does say tends to be very straight-forward.
- Wrench Wench: She started as one of MART's mechanics before she was transferred to the piloting department.
A former idol with strong spiritual awareness, after starring in a movie where she displayed Third Man Phenomenon, Maiko now works as a test pilot for MART.
- Ace Custom: Her Grafdin is a dull yellow color, with reddish highlights. The head is also more geared towards electronic warfare.
A pilotless, sentient giant that stands in the Didarion's way, Angilon is the one of the antagonists of Super Robot Wars DD.
A similar giant allied with Angilon, it is on the relentless hunt for the Didarion.