As we’ve covered before, you can choose the sex of the main character in Fate/Extra. According to a recent preview at Famitsu, this decision will actually affect the story later in the game. More on this below.
There are now 3 possible Servants to choose from. Which you get will be determined by decisions made early in the game. Judging by the screenshots, in addition to the red variant on the classic Saber, it is also possible for you to get a Caster — who seems to be based off a fox girl — and what seems to be the original Archer, who is no doubt familiar to those who know of the Fate series.
This time, the battlefield is a virtual reality world, called the "Serial Phantasm." The game takes place in a setting similar to that of the original game, the campus of Gekkaibara School, and the main portion of the Holy Grail War will take place in this Serial Phantasm; a virtual reality called Seraph. There, the seven Wizards, who have been transformed into spirits, and their Servants fight to the death over the Holy Grail, which can grant any desire to its bearer.