Rai is a recluse plant appraiser, secretly employed by the Higashikata Fruit Company and only known by Norisuke Higashikata IV. Once attacked by the Rock Humans, he joins with Josuke Higashikata in order to protect himself.
Rai is a well-built man with braided dark hair. He wears a jumpsuit with a vine and peapod pattern, as well as a hat with an oversized flap covering the whole back of his head.
Rai Mamezuku is an eccentric and brusque individual with little care for politeness. He is highly analytical and quick-witted in his way of approaching problems. As soon as he learns of what is happening in Morioh and that he is under attack, he takes the initiative in joining with his allies. With a single phone call with Norisuke about Josuke's confusing issue, Rai manages to grasp the stakes for every party involved and see the best course of action for him. He tends to carefully observe his surroundings and verbally takes notes of everything remotely interesting to him; this habit allows him to discern the nature and subtleties of the attack against him. Rai also regularly calculates probabilities, like the chances of someone being safe through selected factors.
Rai is very coldhearted in his methods, repeatedly showing that he has no qualm sacrificing a perceived less important part for a greater goal. His orchard specifically leaves a small part of the culture overriden with predatory insects and disease to better the rest of the orchard, he has no problem cutting off his own hand to save himself, and even puts Yasuho in great danger because he sees her as less important than his own safety.
Moreover, Rai is very cool-headed. Despite being introduced under attack from an unknown ability, he acts calmly despite an open focus on his survival. Once on relatively safe grounds, Rai even takes the time to cook a snack for him, Josuke and Yasuho. When he loses his left hand to a Stand attack, he calmly severs it to preserve the rest of his body.
However, Rai's most noticeable trait is his eccentricity and bluntness. First, he is extremely antisocial. His only relationship is with Norisuke, whom he nonetheless considers a good friend. Rai takes many steps in order to stay isolated, as his home during the summer is actually a support pillar for a skilift, complete with at least a hidden kitchen and a whole mountainside as his orchard; during winter he resides in a villa. Moreover, Rai constantly demonstrates a lack of care for others. He hijacks a bus without a second thought but the repercussions on him, pries on Yasuho's private life and considers his survival as the priority, that of Josuke and Yasuho being second to his. Nonetheless, he seems impressed when Yasuho takes the initiative in covering their tracks and has thought of inviting his guests for a snack while they discuss their next move. It doesn't stop Rai from condemning Josuke when the latter instinctively prioritizes her safety in the midst of an attack and then coldy throw her into the range of the enemy Stand to observe what happens.
- Main article: Doggy Style
Rai's Stand has a currently unknown power, which can create a prehensile bandage-like string from his body in order to grab objects from afar. Rai implies his Stand is not suited for heavy combat, instead relying on Josuke to help protect him in case a battle ensues.
Rai is an expert in horticulture, his profession being a plant appraiser and a fruit grower, implying a great deal of knowledge and experience on plants. He can identify a plant simply from its appearance in a photograph, and has the knowledge on how to properly care for rare plants such as the Rokakaka.
Rai was born into a family of fruit farmers, whose high-class pears were prized goods. However, their cultivating techniques were leaked, leading to a competitor managing to steal an entire crop of pear and bringing down the fruit trees. Thus his parents had to part with their orchards. Blaming his parents, Rai began to live alone in a ski slope, cultivating his own fruits despite the difficulties. Rai met Norisuke Higashikata IV at 17, when Norisuke came to buy his grown strawberries. Impressed by their quality, Norisuke appointed Rai in secret to be his personal fruit grower and appraiser. Rai's existence in the company was kept with the utmost secrecy, with not even Norisuke's own son Jobin ever being informed.
Rai is first shown when Norisuke presents a photo of him to Josuke Higashikata, advising the latter to go find him, as his skills would enable Josuke to recognize the grafted Rokakaka branch.
After communicating with Norisuke in regards to a certain Josuke Higashikata's inquiry about a Rokakaka branch, Rai notices that he is under attack from an unidentified enemy moving underground. Running from his assailant, Rai ends up hijacking the bus which Josuke and Yasuho Hirose are on, formally meeting them and presenting himself in the process.
Rai thus drives to his summer home in the mountains, a ski lift. Discussing with Josuke and Yasuho, Rai manages to find the location of the Rokakaka using photographs of the orchard, and determines that the best course of action for his survival is to work with Josuke.
After a brief snack, the trio is attacked by the unknown assaillant revealed to be a duo of Rock Human and Rock Animal, Urban Guerrilla and his pet Doremifasolati Do. Losing several fingers to a first attack, Rai becomes upset that Josuke has protected Yasuho first instead of him. To observe the enemy, Rai pushes Yasuho down the ski lift, which pushes Josuke to also jump down, although Rai tells him they have to take a fuel tank stored inside one of the lift poles.
Separated from his allies, Rai is attacked by Urban Guerrilla and falls down the lift, heavily injured. However, he's managed to pierce the fuel tank and bring it to Josuke alongside his lighter, which Josuke uses to make Doremifasolati Do and Urban explode.
Afterward, Rai takes with him a vivarium full of moth larvae. When he tells Yasuho to leave and go home, Yasuho refuses and begins to tell her story. Uninterested by her, Rai nonetheless listens when Yasuho theorizes that the strange hair clip which has tormented her may have been a Rock Animal. Thus, he sends her to investigate it.
Arriving at the Higashikata estate through secret underground tunnels, Rai and Josuke stealthily manage to plant the moth larvae in the Rokakaka branch and must now wait 2 days before a new fruit grows.
Their departure is interrupted when they notice the atmospheric pressure growing inside the tunnel. Thus Rai and Josuke decide to go in the open. Seeing the orchard on fire, Rai and Josuke use giant bubble to protect themselves from Ozon Baby's power. Going in the open to take the branch, Rai sees the enemy, Poor Tom, and decides to confront him.
Rai's attempts to break Poor Tom's neck by strangling him with his wired arm proves to be a mistake as touching Poor Tom directly increases Ozon Baby's influence on him. When Poor Tom traps a part of the wire inside a knife sheath to simulate a closed space, Rai succumbs to the pressure, making his body explode.
Despite all observing parties assuming that the plant appraiser was killed by the explosion, Rai was able to successfully utilize Doggy Style in order to disassemble his body rapidly, giving the impression that he was torn to shreds. After the conflict with Poor Tom ends, Josuke discovers a surviving yet disassembled Rai and mourns the loss of the branch, not knowing that Jobin had obtained it covertly.
- ↑ 
- ↑ JJL Volume 16: Mother and Child (Age originally 32 in Ultra Jump)
- ↑ JJL Chapter 59: Dolomite's Blue Lagoon, Part 1