Locacaca

The Rokakaka Trees are a mysterious species of tree which produce rokakaka fruits, featured in Part VIII: JoJolion.

Summary
The exact nature of the tree and its fruit continues to be one of the central mysteries in JoJolion, alongside the circumstances which lead to the creation of the protagonist. It is first mentioned to have existed when Tsurugi explains to his grandfather and Josuke why he trusted Yotsuyu Yagiyama; he had observed the male feeding a dog afflicted with the stone disease, the food having cured it. Although the two are skeptical Josuke is the first to see what appears to be a fruit disappearing into the ocean during his skirmish with Yotsuyu where the latter dies before any solid information can be given.

Using the abilities of King Nothing, the protagonist's group discover that the scent of this mysterious fruit happens to be lingering on Tsurugi's father, Jobin Higashikata, and they resolve to obtain the event record data for his car in order to find out where he has been in hopes of discovering the location.

Yasuho and Tsurugi discover a rokakaka tree in the possession of Yotsuyu's affiliate Aisho and it is then that it's nature of 'equivalent exchange' is demonstrates when an elderly crippled man uses it to regrow his lost limb by sacrificing his own eye sight.

The nature of the fruit and it's miraculous abilities have made it the subject of many people's interest, including Yoshikage Kira for it's abilities to assist in the treatment of his ill mother Holly, and it is noted that after destroying several trees he kept one in his apartment for his personal use. The Rock humans also appear to have a curative interest in the abilities of the fruit as they covet its power and seek to target and kill anyone with information concerning the trees for an as-of-yet unexplained purpose.

Equivalent Exchange
The fruit of the Rokakaka tree follows the same principles of equivalent exchange as the grounds of the Higashikata estate; they are capable of granting anyone who eats it 'something' by taking 'something else' from them. The most faithful example of this concept is when the old crippled man uses the Rokakaka fruit to regrow his lost limb in exchange for his eyesight, both of his eyes transforming into stone and breaking apart soon thereafter. Apparently this process can be repeated as long as someone has a fruit, continuously sacrificing random parts of their own bodies in order to gain back what they had given in the previous instance.

This affect could explain the missing organ pieces of Holly Joestar-Kira, seeing as Karera noted that her son Yoshikage Kira had personally kept a plant for use in treating his mother's illness.

Miraculous curative powers
Perhaps the most intriguing and relevant ability of the fruit to the storyline is the affect it has on those afflicted with the stone sickness; namely the Higashikata family, the Joestar family and the dog Iwasuke. As shown in the case of the latter Yotsuyu was able to 'cure' it if the stone sickness by feeding it a piece of a Rokakaka fruit.

The abilities of the fruit and their correlation to the rock humans and stone sickness make them a constant source of interest to the antagonists of JoJolion, which motivates the conflict between them and the allies of the amnesiac Josuke.