Both players are handicapped so they have a pixel of health, and both have selected Rose as their character.
They are playing best of 9. At the beginning of each round, one of them "serves" by performing Rose's "Soul Spark" move - a half-circle towards on the joystick, and a punch button.
Then, they take it in turns to perform her "Soul Reflect", which can reverse projectiles; this is a quarter-cirlce away on the stick, with a punch button. Whoever fails to time the parry correctly will get hit by the "ball", and the other player will win the round.
Source: Infovore blog