"I would rather be deceived than doubt a friend."Yuki (Sakurai) Giou is the bearer of the Kami no Hikari (神の光 ) "The Light of God" or "God's light". He is the main protagonist and a freshman in high school.
Yuki is a young teenage boy with ash-bronze hair and golden eyes like the rest of the people in Giou clan. He is often noted to be a 'cute' boy according to numerous girls in his school(s).
In his past life, Yuki was a beautiful woman with ankle-length ash-bronze hair and golden eyes as well in her present time. She is always seen in traditional Japanese noblewomen's clothing. (Or white gowns in the anime.)
His special technique is Halo Wall, which puts up a barrier of light around others, protecting them from harm. However, he can't use it for long, because it requires a lot of energy. Yuki's job is to bear the pain and "sins" of the other members.
That's why when he heals the other Zweilts, he takes on their pain. Because of this he often collapses and won't wake for several days. The other Zweilt Guardians feel a great amount of guilt for this. If Yuki takes too much "pain" from the Zweilt, which he has often done in his past lives, he ends up suffering from unbearable fierce pain and dies in madness.
As one who specialises in barriers, Yuki is shown to also be sensitive to other's barriers, able to recognize Shuusei's "sixth barrier," which conceals him from others.
Yuki is good natured, caring, polite and kind. He dislikes being a burden on others - which is shown continuously throughout the series and is very good with young children as a result of his time spent at the Asahi Orphanage. Yuki tends to address others with honourifics, and time after time attempts to make friends with even those who hate him. Takashiro Giou is noted for saying that Yuki is someone that would "Sacrifice themself for the good of others." In his past life, Yuki was jealous of those in long relationships, and was happy when (s)he found Luka and fell in love with him.
As is when Yuki is always reincarnated, the woman who gives birth to him must die, so when Mizuki gave her life so that Yuki could be born, Takashirou took Yuki and placed him in the Asahi Orphanage, in order to protect him from the Giou Clan's elders.
Sometimes, when he touches someone, he's able to read that person's emotions and see that person's past. This caused him to suffer greatly, but he has unexpectedly grown into an unyielding individual.
He doesn't have any recollection of his past life, but he feels an odd nostalgia for Zess, and ends up relying on him quite often. There are a few people and places with whom Yuki has strong memories with that he deems as "familiar."
After he leaves the orphanage and heads off to the Twilight Mansion, he takes the name of "Giou." Yuki is the most important member of the Giou Clan, he's even mentioned as the "master" of the other Zweilts.
"Being locked up isn't a big deal. It's not like I had any freedom in the first place. I know what truly pains me isn't something like this. The most painful thing is--"
In the past, Yuki was actually a female and went by the name Yuuzuki. However, recently, Yuki was reborn as a boy, for the first time. This may be a sign that the never-ending reincarnation circle is actually coming to an end, or that Yuki wished to forget all traces of the past. Right now he can't remember his previous life very much and depends on others for information and recounts of the past.
Yuuzuki-hime was known to have envied those in long-lasting relationships, and having felt ‘very lonely’ until meeting and falling in love with Luka. Yuuzuki is also known to have suffered from frequent nightmares and "there was always an inextinguishable air of sorrow that followed her around."
In her lifetime, it was noted that she was kept and lived away from everyone else and that even the Zweilts couldn't just come and talk to her. 
Her past is one of the great mysteries in the series as everyone seems to be afraid of Yuki remembering his former life. Even Luka seems to be afraid of this and says that if Yuki regains his memories, he won't stay by his side.
From 幸 (yuki) meaning "happiness" or it can also come from 由 (yu) meaning "reason, cause" combined with 貴 (ki) meaning "valuable" or 紀 (ki) meaning "chronicle".
His former name, Yuuzuki, comes from 優 (yu) "gentleness, superiority" and 月 (zuki) "moon".
Luka decided to keep any information related to the past relationship a secret to Yuki, because of his belief that the past reincarnation (of Yuki, not Luka) wanted to forget any and all memories of the past, including ones of Luka. There is another speculation regarding Yuki's reincarnation as a boy believing it is a sign that the fighting will end.
Luka believes that Yuki being reborn as a male is somehow his fault.
Yuki sees Takashiro as an elder brother figure and cares for him despite being lied to by him. Nevertheless, he forgives him and still consider Takashiro an important person to his life. Takashiro's side of things is considerably more complicated and he contradicts himself at times. While he says that he is willing to use Yuki as a tool he also seems to care quite a great deal for him.
Yuki and Kanata met at the orphanage when Yuki was only five years old. The two were close, causing Yuki to consider him an older brother.
Soon, after leaving the orphanage to go to the Twilight Mansion, Kanata tried countless times to convince Yuki to stay with him instead, most notably one time at Ashley's "amusement park" after appearing out of nowhere when Yuki, Luka, and Hotsuma try to save Shusei. Despite his constant pleas, Yuki rejected his invitations and continued on.
After locating Shuusei and saving him, Kanata shows up once more as Reiga Giou, former member of the Giou Clan and current enemy. Kanata was Reiga's incarnation. Yuki is shocked to find this out, questioning Reiga and himself, only getting replies that the name Kanata Wakamiya is discarded.
At the end of that battle, Kanata tells Yuki farewell, seemingly abandoning him.
Reiga is said to hate all human beings, though it is shown that he might still care for Yuki, and is in heavy mental debate whether to kill him off or let him survive.
The two are good friends, with Tsukumo always worrying about Yuki's sake. He likes to hug (
cling onto) Yuki quite frequently.
Touko is fond of Yuki, calling him "Yuki-chan" despite of having only met him, and also stating that he is someone who is too kind for his own good, wanting him to call her "Touko-chan" instead of "Touko-san". She is also fond of hugging Yuki to display her affection to him much Luka's annoyance.
Hotsuma Renjou Edit
Yuki is often worried about Hotsuma due to his brashness and recklessness. Despite Hotsuma avoiding Yuki in the beginning, (due to being afraid of failing in Yuki's expectations of him) Yuki never gave up on him and he helps him to get over with his guilt and fears. Yuki notes that he and Hotsuma are the same in their loneliness. His flames are also incapable of harming Yuki. They have both seriously considered (or attempted) to end their lives, as they discuss in story 14. After which, Hotsuma apologies as he always makes Yuki, "pull a face like that." (in worry.)
In the beginning, Shuusei went along with Hotsuma's standoffishness to Yuki but after Yuki convinced Takashiro to let him risk his own life to save Shuusei, as Takashiro wouldn't hear of it, but due to Yuki's pleading he allowed it. Shuusei probably wouldn't have been alive if Yuki hadn't done this, which he is shown to be quite aware of and tells Yuki that he, "plans on putting my life on the line to repay this favour." He then bows before Yuki, swearing devotion to him.
At first, he wasn't so fond of Yuki but he started to warm up to him later in the anime/manga. In the anime, he was willing to put aside his revenge to save Yuki after Reiga kidnapped him. In the manga, which goes farther than the anime, Kuroto is shown to be quite fond of Yuki and in a show of his tsundere side he asks Yuki if he's alright after being told the truth by Takashiro but then immediately asks him to forget it and says if he's bored he'll play shogi with him. His love for the game was also brought back by Yuki with Kuroto noting that he actually enjoyed playing with him and even lost track of time. They play together once a month. In story 55 after Yuki came back from the main residence in Kyoto, Kuroto tried to welcome him home with a blush but when Senshirou beat him in saying it first, he got very angry with Senshirou. He and Yuki also joined the chess club in school together.
Senshirou has the same unconditional love for Yuki that all the Zweilts have. Yuki tells Senshirou when they are cooking together in story 28, that he gives off a 'motherly feeling.' To which Senshirou has mixed feelings about but it then touched when Yuki also remarks on how gentle he is. Senshirou then gets excited and asks Yuki if he may make his lunches for him and starts asking about side dishes and his favourite foods.
Senshirou tells Yuki that he especially weak against people 'like him.' He then puts his hand on Yuki's shoulders and asks him to "Let me take care of you! I can wash your clothes, sleep with you-" Complete with a sparkly background. Kuroto kicks him away though.
- His birthday is April 21.
- His favourite food is white rice and fish.
- Yuki is noted to be quite good at Shogi and is one of the few people who can rival Kuroto, a professional player. Kuroto remarks that he could enter a national Shougi competition.
- “Please stop. Why… why do you have to fight? Kanata-san, was that really the truth? Were you lying to me this whole time? It’s not true, right? The words you said… that smile… they weren't all lies, were they?”
- "More then enough blood has been spilt… I can’t stand idly by and watch as my friends come to harm."
- "I dreamed a sad dream of a simple life. If this dream can never be a reality, may I never wake up."
- ↑ Story 41