Yushiro is a Demon in Demon Slayer: Kimetsu no Yaiba. He is one of the good demons in the series, who helps our Demon Slayers in killing the demon king, Muzan. He stays mainly with Tamayo and is a friend of Tanjiro and Nezuko.
Yushiro was saved by Tamayo when she turned him into a demon using her exceptional medical skills.
From the first time you see him, you can tell he has a short temper and an arrogant attitude that makes him look down on most of the people around him. The author said that he was too young.

Even in his first conversation with Tanjiro, he makes fun of Nezuko Kamado for being ugly. He is usually shown with a frown, and the only time he smiles is when he is talking about or admiring Tamayo, the girl he loves.
Yushiro Backstory
There is not much shown in terms of the history of Yushiro. All we know is that he was diagnosed with a terminal sickness that could kill him.
Yushiro Turning Into a Demon

He was a human who Tamayo took care of as a doctor. He was sick and weak, and Tamayo gave him the choice of giving up and dying or becoming a Demon and living longer. Tamayo was an expert in the medical field and how the internals of a demon work. She herself was a Demon and could control her urge to kill and eat a human.
He agreed to become a demon and has been with Tamayo ever since, helping her and keeping an eye on her. Yushiro developed a deep connection with Tamayo, and it is shown as he got enraged when Muzan killed Tamayo in the Infinity Castle Arc.
Yushiro Abilities
He is a demon whose strength is unknown. However, he has lived for a long time with Tamayo, who is a demon who seems weak but is actually very strong and could severely hurt Muzan.
Because of this, it is assumed that Yushiro is also a good fighter who can use Blood Demon Arts. Yushiro, on the other hand, is more of a support fighter. He uses his powers to help others see invisible things or hide the fact that they are nearby.
Most impressive is that Yushiro is strong enough to fight with Muzan over who is in charge of a demon, though the Demon Slayers had to break Muzan’s concentration.
Body Modification
Yushiro’s body has been changed by unknown surgeries so that he needs less human blood and doesn’t feel the need to hunt humans. Tamayo said that Yushiro needs less blood to stay alive than she does.
Curse Immunity
Since Yushiro is a demon made by Tamayo, who broke her link with Muzan, he is not linked to Muzan and is therefore immune to Muzan’s control. This means that the Demon King can’t do anything to him, like kill him or read his mind.
However, Muzan was able to spread some of his cells to Yushiro’s hand in order to hurt him and take away Nakime’s control over him.
Acquired Mecial Skills
As Tamayo’s assistant, Yushiro is also a skilled doctor who knows all of her special techniques and drugs. After saving Zenitsu from falling to his death, he was able to use a variety of medicines to stop Kaigaku’s Blood Demon Art from doing more damage.
He was also able to bring Tanjiro back to life when he was almost dead so that he could fight again.
Talented Painter
During Japan’s Reiwa Era, Yushiro became an artist who painted photorealistic pictures of Tamayo on canvas. These paintings have been praised by critics all over the world. Some people think that his paintings are photos because they look so much like real life.
He has drawn at least 812 pictures of Tamayo, and Yoshiteru Agatsuma says that the 812th one, Tamayo with Dark Blue Flowers, was his first love.
Yushiro – Blood Demon Art: Blindfold
Yushiro can use his Blood Demon Art to make paper talismans that can hide or reveal the presence of something. He can get rid of their presence by putting these on things he chooses. If not, he can use it to help someone see better by putting it on their forehead and revealing hidden objects.
Yushiro has used this Blood Demon Art to completely hide the entrance to Tamayo’s clinic in Asakusa and to make it look less suspicious by making walls that don’t exist. But he couldn’t completely hide its existence from Yahaba’s Blood Demon Art, which could track it. With his Blindfold, he can also make himself invisible.
This is also how Yushiro found Yahaba’s hidden arrows and gave Tanjiro the same power. Yushiro’s Blood Demon Art seems to have changed a lot during the Infinity Castle Arc. Not only can he make many of his paper talismans at once, but he can also use them to hide their presence while letting them still see each other.
This gives them a slight advantage over Muzan. As seen with Obanai Iguro and his pet snake Kaburamaru, his Blood Demon Art can let two beings use their vision together to help each other fight better.
Super Support Blood Demon Art
Through the Kasugai Crows, who were also wearing Yushiro’s paper talismans around their necks, Kiriya and his sisters were able to find out where the Demon Slayers were in real-time. This lets them see through the paper talismans on the Kasugai Crows and also tells them what to do.
They have used this link to find out how battles went, how many people died, and how Infinity Castle is constantly changing.
Mind Control
During the Infinity Castle Arc, Yushiro shows off a new part of his Blood Demon Art. With his Blindfold, he can put someone under hypnosis and control their mind and vision. If he uses it on a demon, he can use their skills through them. Like when he used Nakime’s Blood Demon Art to bring the Demon Slayers to the surface as the Infinity Castle fell apart.

He has mental and physical control over them, as shown by the short fight he had with Muzan over Nakime. Both of them controlled her body as they fought for control. Yushiro was able to fight Muzan by absorbing his cells through Nakime. This suggests that Yushiro controls his victims at the level of their cells.
Tamayo X Yushiro
Yushiro blushes and gets quiet when someone says, “You like Tamayo, don’t you?”
Yushiro loves Tamayo and is ready to do anything to keep her safe. He thinks Tamayo is very pretty. He is very crazy about her and will attack and insult anyone who comes near her except him. Yushiro gets enraged when he realises that Muzan killed Tamayo, and his suddenly longer fangs show this.
Yushiro is still alive and well in the modern world. He works as a painter. He is always painting pictures of Tamayo because he still loves and respects her very much after all these years.

Final Thoughts
Yushiro is one of the demons who doesn’t kill any human. He is able to sustain himself by other forms of consumption. It included dead animals, humans or their blood. He helps significantly during Infinity Castle Arc.
You can even say that he was the reason that Nakime, the Upper Moon Rank Four died.