Yuki Giou is the bearer of "The Light of God" or "God's light". He is the main protagonist and a freshman in high school. Yuki is a kind, caring, polite and good-natured boy. 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 honorifics, and time after time attempts to make friends with even those who hate him. Takashirou Giou is noted for saying that Yuki is someone that would "Sacrifice themselves 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 Crosszeria and fell in love with him.
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.