Sage Date (Date Seiji in the original Japanese) is a member of the Ronin Warriors and considered the most mature and aloof member of the team. One of the key moments for this character takes place in the CD drama Korinden, when he questions whether or not he wants to be a Ronin Warrior.
Sage comes from a very traditional Japanese family, in which the women hold the power. He has a father who is a police officer, a mother, grandmother, grandfather, older sister Yayoi, and younger sister Satsuki. Satsuki is the most "normal" of the Date family and doesn't use proper Japanese language like her siblings.
In the OVA Gaiden, Sage was captured by Shikaisen and the Mad Scientist; his Halo Armor was used to kill people in New York, one of them being Runa's brother.
Sage wears the Halo armor, called Korin (literal translation: holy aura) in YST. His Virtue is Chi (Wisdom), which was changed from Rei (Courtesy) in YST. His elemental affinity is light. Sage fights with a nodachi, a Japanese broadsword. His surekill is the Thunderbolt Cut, called Rai Ko Zan (Lightning Strike) in YST. His thunderbolt has him gather a large amount of energy to his sword, and despite the name it's sometimes used as a thrust attack. It can also manifest as a burst of energy beams.
There is an interesting little story about Sage and it seems that he was vice-president of the Kendo club at his high school in ninth grade and the president in tenth grade. Because of the battle with Talpa (Arago) which occurred in the spring (that would be his second resurgence), Sage did not attend the Kendo tournament. A young man named Shingo (apparently a friendly rival of Sage's in the sport) won the championship that year and later wrote a letter to Sage, hoping that they'll meet at next year's tournament.
It was in this letter that Rowen and Kento got the idea to cut Sage's hair. Shingo had written that Sage didn't look bad with both eyes and asked him why he didn't cut his hair. Rowen and Kento chased Sage with scissors. They didn't read the rest of the letter where Shingo speculated that maybe Sage's victory was due partly to how intimidating Sage looks with both eyes showing. Sage is voiced by Michael Donovan in the English dub.
Like Ryo, Sage's family name Date, comes from a real-life samurai called Date Masamune.