Vinegar Doppio

Doppio appears as a fairly slim yet fit young man, described as appearing too young to have children. He has freckles, contributing to his boyish looks, and light-colored irises that disappear when he is not in control of the body. His hair is tied into a neck-length ponytail by a weave-like braid; the front hair is left loose and sweeps over to one side lock, the position and length of which is portrayed inconsistently.↗↗

His clothing consists of a light-colored sweater with gash-like openings on it that leave the midriff exposed and a loose pair of jeans with studs covering the thighs and sides of the ankles. Doppio also wears a black mesh shirt underneath the sweater.↗

Doppio is a much more regular person in contrast to Diavolo: friendly, honest, and a bit cowardly. Doppio regularly hallucinates random objects as "phones" with which he talks with his alter-ego, not knowing that they share the same body.↗

Doppio mostly behaves in a good-natured way, being friendly and polite. After borrowing a toy phone from a child while taking a plane, he apologizes for taking too long. He cares for insects, risking his life by jumping in front of a truck to save one when a kid was about to catch it. Whenever attacked, Doppio automatically reverts to a state of true fear and submission, often choosing the safest option such as comply with his aggressor's demands. He believes himself to be unlucky, which provides an ironic contrast to Diavolo's good fortune.↗↗↗

Fiercely loyal to his boss to a point of attempting to fulfill the mission first and foremost, Doppio is somewhat resourceful although Diavolo has to help and counsel him from time to time. Despite this, Doppio has a sense of pride. During his battle against Risotto Nero, Doppio refuses to leave the battle or have his boss step in, remaining and doing all he could to find a weakness in Risotto's Stand, Metallica. He shares his alter ego's collected nature when in battle, and while his first actions are usually panicking and screaming, he soon and very quickly calms down, carefully using his tools to identify the enemy and their powers.↗↗

Stand

Due to sharing the same body with Diavolo, Doppio is at least partially capable of using King Crimson, notably its Epitaph, a sub-ability of King Crimson, as well as King Crimson's arms. However, Diavolo informs Doppio that he’s only lending him these abilities. As such, it allows Doppio to see ten seconds into the future and perform powerful strikes the same way Diavolo does. According to Diavolo, however, Doppio cannot use King Crimson's signature ability unless Diavolo himself takes over the body.↗↗↗

Double Personality

Doppio and Diavolo are two souls that inhabit the same body. As a result, they can switch their personalities as well as their physical appearance. Compared to Diavolo, Doppio appears a lot younger and is described by a fortuneteller as looking too young to have children. Diavolo appears to be a lot taller, as well as more muscular. When he takes over, Doppio's freckles disappear, his voice deepens, and his hair is seemingly a different length. According to Diavolo, it takes a couple of seconds for him to completely take over Doppio's body.↗↗↗↗

Diavolo seems to be able to manipulate Doppio's memories, as Diavolo remembers everything and can see everything that happens to Doppio but not vice versa, although it's unknown how much of this is based on Doppio's possible poor memory.↗

Doppio can communicate with Diavolo through any kind of object while not in control, making the underboss believe he is another person altogether. Doppio can always hear his alter ego's voice through the object. Whenever Diavolo wants to talk to him, Doppio subconsciously making a ringing noise and grabs a random object in his vicinity to act as a phone. Doppio also always carries a broken or dismantled phone headset.↗

Chapter 456: 5 Plus 1 (Mentioned) Mentioned only↗

Chapter 523: The Mystery of King Crimson, Part 6 (Voice only)↗

Chapter 541: Storm Warning in Sardinia Island!↗

Chapter 542: My Name is Doppio, Part 1↗

Chapter 543: My Name is Doppio, Part 2↗

Alter Ego

Diavolo: While Doppio never learned the truth between themselves, he highly respects Diavolo and always called him "Boss" - though whether or not Doppio knew Diavolo's name is unknown. Doppio also seems to be Diavolo's gofer, something he takes pride in considering how loyal he was to a point of stubbornness, and he seemed heed most of Diavolo's orders when he remembered them.↗

Enemies

Risotto Nero: Both of these characters have a mutual dislike for each other. Risotto dislikes Doppio simply because he is connected to "the boss" and vice versa because Risotto is looking for the boss. As Risotto continues to try to kill Doppio, his resolve develops to the point that Doppio is willing to risk his own life to kill Risotto in order to protect himself and his boss.↗