Burning Fruit

Burning Fruit exists purely to unlock the evolution of a single Unit, Flame Emperor. Its in-game description simply notes that it's obtained from completing Flame Emperor's unit quest, and it has no use outside of that evolution.

Alongside Burning Fruit, evolving Flame Emperor into Flame Emperor (Reincarnate) also requires the base Flame Emperor Unit, Red Sprite, Yellow Sprite, Rainbow Sprite and a Gold cost, so it's the centerpiece item in a larger evolution material list.

Burning Fruit drops from the Evolution Quest tied to Flame Emperor, listed in-game as the Fire That Spreads quest stage. This quest is only accessible once a player owns a Flame Emperor Unit, since it's specifically built around that Unit's storyline.

There is no shop, trader or general stage drop for Burning Fruit outside of this quest, which makes it a targeted farm rather than something picked up passively.

Burning Fruit is only relevant to players who own and want to evolve Flame Emperor. Since it's Mythic-tier and quest-locked rather than a random drop, it acts as a gate that confirms a player has actually cleared the Flame Emperor Evolution Quest before letting them push the Unit further.

Outside of collecting the other evolution materials, Burning Fruit itself doesn't need to be farmed in bulk since only a single copy is required for the evolution.