Daichi Tanaka (田中大地 in Japanese) was the father of Leiko Tanaka and Noriko Null's grandfather.

A very rich and extremely powerful man, he founded the Scion Corporation as a front for his connections with the Yakuza. He also used the Core and made business with Eris. He was known for being cold and ruthless, especially after the death of his two sons.

When Leiko traveled to the United States and got herself pregnant in order to unlock the Heart Of The Universe, Daichi tracked her and arranged the falsification of the birth certificate of his granddaughter.

He was killed under orders of Leiko 2 years before Noriko Null was chosen by Athena as Earth's protector.