GOZO means the reward system for some events.

There are two types, GOZO and Rare GOZO.

GOZO system is applied in some events like Colosseum and Raid Battle and the amount and type of GOZO you can get is depending on your performance in the event.

Extensions, Materials, and Cp can be obtained from treasure chests distributed by the GOZO system, and Rare GOZO is more likely to yield higher rarities and larger numbers of items.