PVP
In CrossWorlds, players are able to challenge each other to PVP duels.

Mechanics
PVP duels take on a best-of-9 format, with the first player to win 5 rounds claiming victory in the duel. After each round, both players are healed, although the winner only receives half their total health in healing.
It is impossible to use consumable items during a PVP match, although it is possible to cheat this by eating an item before starting PVP. Damage dealt by both players is reduced during PVP to prolong the match.
When a PVP match is started, temporary walls are summoned around the dueling players to form an arena, and any other players caught in the arena are teleported out.
It appears to be possible to start a PvP duel anywhere, but there are special areas set aside for this in Rhombus Square and the Arena.

In CrossCode
Lea is challenged to PVP several times over the course of CrossCode. She is never seen issuing a challenge, and may be unable to do so, due to the limitations on her account.
List of PVP matches:
- Apollo in Bergen Trail
- Apollo in Maroon Valley
- Apollo in Gaia's Garden
- Shizuka in Old Hideout (up to 3 consecutive duels)
- Lily arena duel, PvP vs Lily (A New Home DLC)
- Apollo in Rhombus Square (A New Home DLC)
- Apollo arena duel, PvP vs Apollo (A New Home DLC)
- Shizuka arena duel, PvP vs Shizuka (A New Home DLC)
There are other battles that resemble PVP duels in some ways, but do not actually use the CrossWorlds PVP system. The fights against the Blue Avatar are one-on-one duels against another player, but do not feature the same mechanics as a PvP duel. The arena fight against Sao in the A New Home DLC has a similar five-round format, and takes place in a PvP arena, but otherwise does not follow the conventions of a duel; in particular, dying will cause Lea to lose the entire duel, not just a single round.