Proof

The Proofs are sets of key items which appear in Kingdom Hearts II Final Mix and Kingdom Hearts III, which are obtained after completing specific side-missions.

Kingdom Hearts II Final Mix
The Proof of Connection is obtained by defeating the Lingering Will, the Proof of Nonexistence is rewarded after defeating all of Organization XIII's Replica Data, and the Proof of Peace is given after appeasing the entire Mushroom XIII. Possessing a Proof grants Sora a crown costume modification.

Kingdom Hearts III
Added in update 1.04 on April 23, 2019, the Proof of Promises is obtained by photographing all 90 Lucky Emblems and clearing the game, while the Proof of Times Past is obtained by clearing the game in Critical Mode. Proofs carry over through New Game+.

As of version 1.07, released on January 22, 2020, the Proof of Promises and Proof of Times Past can be exchanged at the Moogle Shop for the Oathkeeper and Oblivion, respectively.