Rank-Up (ランクアップ Rankuappu) is a method used to Summon higher Rank Xyz Monsters in the Yu-Gi-Oh! ZEXAL anime. It was first seen in the Duel between Yuma Tsukumo and the Barian pawn Fender, who used "Rank-Up-Magic Barian's Force" to Rank-Up "Mechquipped Angineer" into "CXyz Mechquipped Djinn Angeneral". From then on, the Barians and their pawns, as well as Yuma Tsukumo, Number 96: Dark Mist, and Eliphas easily Rank-Up with use of the Rank-Up Magic archetype and "Chaos Field". Additionally, in the manga, Kyoji Yagumo uses Rank-Up as a means of bringing out his other "Numbers" instead of using Rank-Up to evolve them into "Number C" by using the card called "Rank-Up Spider Web".
When a regular Xyz Monster is Ranked Up, it usually results in a "CXyz" monster. When a "Number" is Ranked Up, it becomes a "Number C".
Chaos Xyz Evolution
This was the first method of Ranking-Up seen. It is typically used by Barians and their brainwashed pawns.
This type of Rank-Up has only been seen being used by cards with the power of Chaos, such as "Rank-Up-Magic Barian's Force", "Rank-Up-Magic Limited Barian's Force", "Rank-Up-Magic - Numeron Force" and "Chaos Field". All "Number" monsters Ranked-Up in this method become "Number C" monsters, and other monsters become "CXyz" monsters.
Double Rank-Up (ダブルランクアップ Daburu Rankuappu) , a.k.a. Rank-Up Xyz Evolution, is in essence the same method, although rather than merely Summoning a monster 1 Rank higher, it allows one to Summon an Xyz Monster 2 Ranks higher than the target. This can currently be achieved only by using the card "Rank-Up-Magic Astral Force".