Allies In Diamond Is Unbreakable

Nijimura's Father 

Crippled and deformed by one of DIO's implants after his death, he is cared for by his sons, Keicho and Okuyasu Nijimura. He is unable to communicate above a basic, animalistic level. Keicho assumed that he is unable to recognize his two sons and that he does not seem to possess self and environmental awareness. He seems effectively immortal and possesses extraordinary healing capabilities.

Joseph Joestar 

As the grandson of Jonathan Joestar, Joseph is a natural-born Ripple user and eventual Stand user, wielding the psychic photographic Stand, Hermit Purple. He has considerably mellowed out, having lost much of his aggression and laziness. He is also the second most recurring JoJo in the series after his grandson Jotaro Kujo. He is also the father of Josuke Higashikata, the protagonist of Diamond is Unbreakable.

• Hermit Purple: Hermit Purple's vines are relatively weak, but they provide Joseph with considerable divination ability, enabling him to divine and materialize any type of information, such as an image, a location or even thoughts. Joseph also can use the vines as ropes, whose movements he can control at will. 
  
• Divination: Hermit Purple's main ability is to divine information. By using any object or material in conjunction with Hermit Purple, Joseph Joestar can display any information he wishes to see. He can produce psychic photographs by destroying a camera, produce live psychic videos on a television and conjure a map out of dust on an unpaved road, with precision on the location of a desired item.
• Ripple Transmission: Joseph has shown the ability to transmit the Ripple through Hermit Purple as an extension of his body.

Tamami Kobayashi 

Tamami is a petty scammer who tries to swindle Koichi but is eventually neutralized. He subsequently becomes a minor ally and works legitimately as a debt collector. His Stand is The Lock.

• The Lock: When activated, it grows a physically heavy lock from the chest of its targets when Tamami is able to have them experience the feeling of guilt. It is odious, but surprisingly dangerous because it can push people into committing suicide. 
  
• Guilt Increase: By making someone feel guilty, Tamami can then summon The Lock which appears inside the victim's chest. Afterward, their guilt is multiplied continuously and can add up with other accusations, represented by The Lock growing bigger and heavier.
• Lie Detection: The Lock is shown to be capable of detecting dishonesty in a person.

Toshikazu Hazamada 

Hazamada is initially a malevolent Stand user given power by Keicho Nijimura before being neutralized by Josuke Higashikata and Koichi Hirose. He subsequently becomes lawful and befriends Koichi. His Stand is the manipulating doll, Surface.

• Surface: It is able to copy any individual's appearance almost exactly and in certain distance-related circumstances, is able to dictate their movement. 
  
• Mimicry: Surface's primary ability is to copy the appearance of another person. If the mannequin faces someone, it will perfectly copy that person's appearance, voice, and mannerisms, down to the fingerprints.
• Forced Synchronization: When Surface impersonates someone, it can force that person to imitate its movements.

Yukako Yamagishi 

Yukako is a high-school student besotted with Koichi Hirose. She originally tries to kidnap Koichi before being neutralized and eventually starting a mutual relationship with him. Struck with the Arrow by Keicho Nijimura, Yukako is a Stand User who freely manipulates her hair through Love Deluxe.

• Love Deluxe: Lending versatile life to her long hair, this stand enabling Yukako to spontaneously extend her hair, grasp heavy objects securely, and strike, smother or infect human targets.
• Hair Manipulation: Love Deluxe is bound to Yukako's hair, allowing it to grow to various lengths and move with considerable strength and dexterity. It has a range of about 10 meters.

Shigekiyo Yangu 

Introduced as a kid using his Stand, Harvest, to collect money throughout the town, Shigechi befriends Josuke Higashikata and Okuyasu Nijimura. However, he is soon killed by Yoshikage Kira, prompting Josuke Higashikata and his friend's search for the murderer.

• Harvest: Harvest is a long range colony Stand. It possesses the following basic characteristics: 
  
• Persistence: Each of Harvest's 500 units can be destroyed with ease, but with little to no effect on Shigechi himself, as the damage is divided by 500. It makes him more resilient than average in a fight.
• Strength in Numbers: An individual unit of Harvest is fairly weak. In combat, Harvest will swarm someone and attack weak points.
• Harvesting: Shigechi can command Harvest to search for and collect any particular type of item, provided it’s light enough for Harvest to carry and bring back to him.
• Hypodermic Needle: Each individual Harvest possesses a needle with which Shigechi can inject any liquid directly into his opponents' bloodstream.

Mikitaka Hazekura 

Mikitaka Hazekura, also self-proclaimed as Nu Mikitakazo Nshi. With Stand-like powers, Mikitaka professes to be of extraterrestrial origin. His shapeshifting ability is named Earth Wind and Fire.

• Earth Wind and Fire: Designated as the effect of a Stand-like power, Mikitaka may transform any part of or his entire body into almost any object, as long as the object isn't too complex.
• Shapeshifting: Earth Wind and Fire allows Mikitaka to transform into any object. Although he can theoretically perfectly replicate objects, Mikitaka is subjected to several limitations.

Yuya Fungami 

Yuya is a motorcycle gang member who was made into a Stand User by Yoshihiro Kira and was then prompted into attacking the Joestar Group. He lures Rohan into a trap and later pursues Josuke in a high-speed road chase with his Highway Star. Yuya later assists Josuke and Koichi as an ally and friend in the fight against Terunosuke. He is shown with the rest of the group when Reimi departs.

• Highway Star: Yuya's mainly automatic Stand which tracks targets at a speed of 60 km/h in order to efficiently absorb their vitality. This allows Yuya to recover from injuries at a significantly faster pace. 
  
• Room Creation: Highway Star's first witnessed power is a rather odd ability to create a room and lure victims into it. Anyone who enters the room is targeted by Highway Star, who then acquires their 'scent'. Once it has hold of its victim's scent, it begins to relentlessly chase them anywhere at a constant speed of 60 km/h.
• Enhanced Sense of Smell: Highway Star possesses a superhuman sense of smell that Yuya himself sports. While Highway Star can acquire someone's scent and automatically lock onto their position, Yuya's own nose is subtle enough to pick up and distinguish faint odors.
• Body Dismantlement: Highway Star can section itself into many slices as it flies at high speeds, breaking apart into flat horizontal segments shaped like footprints that move independently of each other and then reassembling itself piece by piece.
• Life Force Theft: Highway Star's main ability is to suck life energy or nutrients, from its victims when any part of it touches the target and transfer it to Yuya in order to heal him.

Antonio Trussardi 

Tonio is a professional chef of Italian origins working in an Italian restaurant named Trattoria Trussardi, at the edge of the town of Morioh. He is also a Stand User who uses his Pearl Jam to enhance his cooking.

• Cooking: Tonio is a pre-eminent chef specialized in Italian cuisine. He is able to create delicious dishes using the highest grade ingredients.
• Esoteric knowledge: Tonio Trussardi has studied many miscellaneous esoteric healing techniques such as palm-reading to diagnosticate ailments. He also mentions having studied Chinese medicinal art, Amazonian medicine, and researched various African healing herbs. It helps him selecting obscure ingredients for his dishes.
• Pearl Jam: a swarm of vegetable-like creatures that infuse themselves into Tonio's dishes, and increase the healing potency of the dishes to supernatural levels. 
  
• Curative Cooking: Pearl Jam has the ability to infuse itself into Tonio’s culinary creations and cure the consumers ailments upon ingestion by enhancing the natural curative properties of the ingredients in a particular dish.

Aya Tsuji 

She is the manager of and sole aesthetician in the Cinderella beauty salon. When Yukako Yamagishi enters her salon, Aya modifies her face to be more attractive. Aya is a Stand User, and works through her Cinderella.

• Cinderella: This stand is able to change a person's appearance in part or in total, either temporarily and through the condition of the affected person applying a special lipstick every 30 minutes or permanently. Cinderella's abilities are centered around cosmetic work and are exclusively used in that regard. 
  
• Body Part Replacement: Cinderella is able to replace select parts of one's outer body by creating a replacement for it from the slots on its hand and then sliding the hand into the body to replace said part.
• Permanent Body Replacement: In the case someone wants to permanently modify themselves, several additional rules apply.

Shizuka Joestar 

Shizuka is a baby found on the side of a road in Morioh by Joseph Joestar, who subsequently adopts her. Incidentally, she is a Stand User who can turn invisible thanks to her Achtung Baby. Her Stand activates when she is startled, frightened, or distressed, rendering her invisible.

• Achtung Baby: Shizuka's Stand, Achtung Baby, renders her invisible as well as everything inside a certain sphere around her when particularly distressed.
• Invisibility: Achtung Baby has the power to render its user Shizuka invisible. In cases of great distress, it will also cause everything within a certain distance of her to become invisible.

Ken Oyanagi 

Ken is an ordinary child made into a Stand user by Yoshihiro Kira and prompted into challenging Rohan Kishibe in a game of rock-paper-scissors in which the latter must gamble his own Stand. Ken's ability is named Boy II Man.

• Boy II Man: It is a Stand who enables Ken to steal someone's Stand when the latter participates in a game of rock-paper-scissors 5 rounds long with him and loses. Each round lost causes the victim to lose a third of their power to Ken. An ultimate win from the victim's part gives back the full Stand. 
  
• Energy Theft: Boy II Man's power is to steal the energy of an opponent whenever Ken beats them in a game of Rock Paper Scissors.

Toyohiro Kanedaichi 

Kanedaichi is a hermit living inside a transmission tower, which is revealed to be his own Stand, Super Fly. Trapped and wishing to escape his tower, he draws Josuke inside his home and subsequently battles him, Okuyasu and Mikitaka. His real name and identity are unknown.

• Super Fly: It is an automatic Stand that imprisons its user, Toyohiro, inside it, making it a nuisance. Its power of damage reflection means that it is powerful and invulnerable, but anyone is free to exploit the pylon when fighting inside it.
• Occupant Restraint: Super Fly's defining ability is that it imprisons one occupant inside it. It is mentioned that the energy of the sole prisoner is how it sustains itself.
• Damage Reflection: To protect itself, Super Fly absorbs and reflects any damage done to its structure and back at the attacker. Furthermore, if the energy blasts hit the tower itself, they simply rebound against it until it hits someone or the energy escapes.