Sol Kuonji is one of the 9 siblings in the Kuonji family. Sol and Marè are twins and the only two confirmed related by blood
Sol so far seems childish, mischievous and free spirited. Upon debuting in the manga, he jumps out from behind a tree onto Tsukito and asks Stella who Tsukito is to her and if he can kill the boy. He also pays close attention to the smallest of movements, like when Mare stole Stella's handkerchief despite the latter not noticing at all.
It's later revealed though that while his personality seems opposite of Marè, it is in fact rather similiar to his twin's personality in the essence that other's feelings don't matter.
In Sol's home country of Russia He and Marè were orphaned twins. They often took refuge in a chruch until their paternal grandmother took them in for the sole purpose of raising one to be her heir. Their grandmother revealed that their mother was a beautiful maid whom 'bewitched' her son which resulted in the birth of the twins.
At first the grandmother put most of the training of being an heir onto Sol, keeping him busy with private tutors as well as keeping him away from Marè. Since there wasn't much of a need for both twins since only one could be the heir. The only reason the grandmother kept Marè around was because she could control Sol using Marè's safety & wellbeing as leverage.
One day when Sol was left to his own devices he happened accross the bag of his mother's that the grandmother had taken away from Marè. He wanted to make Marè happy so he went and placed it on the doorstep of the house Marè was locked up inside. However Sol was unaware the door was unlocked, he witnessed the stray dogs attack his twin from behind a tree. While he wanted to and almost went to help his younger twin, the grandmother's pitbull grabed his sleeve. She threatened to order her dog to attack him if he went to Marè's aid.
Sol blamed himself for what happened to Marè ever since that day. He also burned down the mansion of their grandmothers after witnessing the aftermath of their grandmother's murder. He did this to hide the evidence in an attempt to protect Marè. He's the one who took the offer of the Kuonji's so he and Marè could escape without being caught for their crime.
Finding Marè's dead charred body, Sol refused to accept it due to the fact he never fulfilled his duty as a 'big brother' to project Marè. To the point where he becomes serious in this 'killing game', since if he wins he can get to successfully revive Marè or so it seems.
After finding Marè's charred body he goes to Melm and requests a doll in Marè's image. He carries around this 'doll' with him afterwards. Treating it as if Marè is still alive.
He eventually trapped Stella in his estate on the Kuonji's grounds, the chruch to be specific. Holding Tsukihito hostage with a bomb beneath the white haired boy. Here is where Sol informs Stella of his & Marè's past. We also learn that his goal is not to revive his twin either, stating it'd be an insult since no one is revived without scars unless they are the victor of the killing game. After Stella beats Sol's bluff by using the Jabberwocky to get a device that uses nitogren to give his arms frostbite to defuse the bomb or so she thought for it was actually a timer based one. While she tried to get all three of them out of the chruch, Sol meets his demise by chosing to stay within the chruch, where he apoligizes to the spirit of Marè, informing her that he did indeed leave the bag on the doorstep that day but didn't know the door was unlocked nor intended for her to be harmed.
- Like Marè, Sol's name is Latin for"sun", his kanji "太陽" meaning "sun".
- Just like Marè, Sol can maniputlate fire to his will.