Yushiro has the appearance of a young boy with pale skin and bright lavender purple eyes. He has short hair that is neatly styled and vertically shaded from a dull green to black. Yushiro wears a button-up shirt under an all-white kimono and dark blue pants.
From his first appearance, it is evident he has a short temper and holds an arrogant attitude, looking down on most around him. His first conversation with Tanjiro even begins with him insulting Nezuko Kamado for being an eyesore. He is usually depicted with a scowl on his face and rarely seen smiling unless when speaking about and or admiring Tamayo, who he is in love with. He only cares for Tamayo and hates when others get in the way of his spending time with her and dislikes not being by her side for even a minute. In fact, he cares so little for others (and only for Tamayo) that while Tanjiro and Nezuko were fighting two demons who were trying to kill them, Yushiro suggested to Tamayo that they use Tanjiro and Nezuko as decoys to run from the demon, a suggestion that horrified Tamayo. Though Yushiro claimed he was joking to appease her, it is evident he genuinely considered it. He hates when others get too close to Tamayo, express even the smallest bit of attraction, or he perceives that someone insults her. He himself tends to fawn over her a great deal. He seems to be insulted when Tanjiro suggests that all demons have a hard time controlling their desire to feast on humans, asking Tanjiro if he thought all demons were that bloodthirsty. Despite this, he can show respect towards others, as he did take back his comment about Nezuko being an eyesore and called her pretty and also covered Tanjiro's mouth to prevent him from inhaling Tamayo's perfume, which is poisonous to humans.
Yushiro was a human who was under the care of Tamayo as she was practicing as a medical practitioner. He was in frail state fighting a disease when Tamayo gave him the choice of succumbing to his illness or to live longer as a Demon. He agreed to become a Demon and has since stayed by Tamayo's side serving as an assistant as well as her guard.
Yushiro and Tamayo first appear to Tanjiro after he encounters Muzan for the first time, though he looks noticeably irritated. Yushiro is later seen waiting for Tanjiro outside a food stall. He then proceeds to insult Nezuko, to which Tanjiro gets upset. Yushiro ignores him and proceeds to lead him to Tamayo's clinic, where she is treating the woman who was injured. When Tanjiro asks Tamayo whether treating humans is uncomfortable, Yushiro hits him and tells him off for it, but Tamayo chastises him gently. He then sits quietly until Tanjiro, who is surprised that Tamayo had turned Yushiro into a demon, asks for Tamayo's age, to which he reacts and punches Tanjiro again. She reprimands him again, more severely this time, and he then sits quietly.
He is the first to notice the Susamaru and Yahaba when they attack the house and protectively covers Tamayo when Susamaru's handball breaks through the roof. However, his head gets taken off right after he realizes that the demons are Muzan's underlings. While Tanjiro fights the two demons, Tamayo holds his body as Yushiro regrows his head. Yushiro begins yelling about how the more people are hidden under his Blood Demon Art, the harder it is to hide. He also yells about how he hates it when his time with Tamayo is interrupted.
Yushiro and Tamayo get hit by the ball several times before he tells Tanjiro to avoid the arrow patterns. He sends a paper talisman to Tanjiro and shares his sight via said paper talisman.
Following the final battle against Muzan, Yushiro would later become the last known survivor of the Demon race. In time he would dedicate himself to a life of art and become a world famous painter in the present day under the name of Yushiro Yamamoto, known for his paintings of Tamayo to wide critical acclaim. He is known as a mysterious figure with an infamy for his aggression to reporters seeking to interview him.
He has drawn at least 812 artworks of Tamayo with the 812th work, Tamayo with Dark Blue Flowers, being by Yoshiteru Agatsuma's account his first love.
Yushiro is in love with Tamayo and is willing to do anything to protect her. He finds Tamayo very beautiful. He is very obsessed with her and will attack and insult anyone who comes near her but him. Upon sensing Tamayo's death at the hands of Muzan, Yushiro becomes enraged, evidenced by his suddenly elongated fangs.
In the modern era, it is evident that Yushiro is still alive but takes an occupation as a painter painting pictures of Tamayo since he still has great respect and loyalty to her after all these years.
At first, Nezuko is threatened by Yushiro's presence as she senses that he is a Demon; however after she realizes he shows no ill intent or harm towards her or Tanjiro, she no longer perceives him as a threat and stops being wary around him.
Yushiro initially sees her as "unsightly," due to his personal belief that all Demons are disgusting and grotesque with the sole exception being Tamayo, his master and the object of his undying love. However, after they fight side-by-side during the attack on their hidden clinic by Yahaba and Susamaru, he revises his opinion of her, calling her beautiful. Nezuko likewise sees Yushiro as one of her younger siblings and begins patting his head, much to his dismay.
At first glance, the two don't get along well, as Tanjiro had asked how old she was, and they fight. But later on in the story, they grow respect for each other, going so far to tell Tanjiro how much he admired Tamayo.
Yushiro is a Demon of unknown strength, although living for a long time under Tamayo, who is herself a deceptively strong demon who could severely weaken Muzan, it is assumed that Yushiro is a competent fighter as well. Yushiro for his part, however, is more of a support combatant aiding others with his powers to allow them to discern invisible things or otherwise mask his allies' presence. Most impressively, Yushiro is strong enough to wrestle for command against Muzan over a Demon, albeit with the help of the Demon Slayers to interrupt Muzan's concentration.
Curse Immunity: As a result of being a Demon created by Tamayo who severed her link with Muzan, Yushiro is by default not linked to him and as such immune from Muzan's control, preventing the Demon Lord from exerting any influence over him, such as destroying him remotely or reading his thoughts.
Body Modification: Through unknown surgical procedures, Yushiro's body has been adapted to live with minimal human blood consumption and no drive to hunt humans. Tamayo stated that Yushiro requires less blood than she does to sustain himself.
Medical Skills: Being Tamayo's aide, Yushiro is also an expert medic being familiar of her special techniques and drugs. He was able to resuscitate a nearly dead Tanjiro to health, allowing the latter to be able to fight again.
- Sight Manipulation: He can completely hide the entrance to Lady Tamayo's clinic in Asakusa, but couldn't mask it's existence completely from Yahaba's Koketsu Arrow. To counter, Yushiro could reveal Yahaba's hidden arrows and bestow this power to Tanjiro as well. Yushiro also possesses the ability to turn invisible using this ability.
- Presence Manipulation: Later on during the battle against Muzan, it seems his powers have developed considerably, allowing the Demon Slayers to mask their presence and see one another while using his papers, granting them the means to achieve an advantage against the Demon Lord himself.
- Mind Control: Yushiro is able to put an individual with his blindfold under hypnosis and take control of them. If used on a Demon he is able to make use of their techniques through them. His control over them is not only mental but also physical, as evidenced by his brief contest with Muzan over Nakime, where both parties controlled her body as they wrestled for command. Yushiro impressively was able to fight Muzan absorbing his cells through Nakime, thus implying Yushiro manipulates his victims on a cellular level. Yushiro requires to be in proximity of his target to control.
- If someone tells Yushiro "You like Tamayo-san, don't you!", he gets super blushy and quiet.
- Yushiro was ranked in 17th place as of the first character popularity poll with 145 votes.
- Yushiro has a diary in which he writes about how wonderful Lady Tamayo is.
- Both of Yushiro's voice actors, Daiki Yamashita and Kyle McCarley, also share the roles of Narancia Ghirga from JoJo's Bizarre Adventure: Golden Wind, Genta Doi from Hi Score Girl and Hal Clark from Astral Chain.
- By Chapter 204 and 205, Yushiro and Chachamaru are presumably the only Demons still left alive.
- (To Tanjiro Kamado) "Tanjiro! Your kid sister... is a beauty."
- (To Kaigaku) "Someone who never gives to others will someday become unable to receive anything from them. Only wanting is, in the end, the same as having nothing... because one is unable to create anything. Such a pity to die alone." 
- (To Muzan Kibutsuji) "Muzan. You have committed the gravest sin in the world. You have taken Tamayo-sama away from me. Now get on your knees and repent!! Right now, I am going to erase you from the face of this earth!!"