(This is for the fanfiction "Crossover Together". Info may change from canon information)
Yugura Kagayaki, otherwise known as Twilight, is a returning student to the Orora High School, apart of class 3-C of her 3rd year, having to repeat the year due to moving.
Twilight is a smart girl, often looking towards pure logic, and will try her best to study things that can't be easily explained. When something abnormal presents itself, she either becomes completely freaked, or very fascinated, which shifts completely depending on what she comes across. She can be sweet, but, tried to keep things neat and scheduled as much as she could.
During her childhood, she was sent to an all-girls school, where she first met and befriended Nagisa Shiota. The two became close friends after a while, until Twilight had to move away. Despite this, she still kept in contact with Nagisa most of the time, which was how she found out about him running away from home.
Her family moved back into Tokyo after several years, and she soon found her old friend at the same school she was attending. She and Nagisa briefly catch up with eachother before their first day of school began. Twilight herself never got word about the demon situation until she met with Aladdin, finding his magic very fascinating. She started to grown concerned though when Aladdin told them about possible demons roaming around, only growing even more so when she heard that Nagisa had killed the Jizo. She began to investigate on the matter a little bit, and she discovered that an Ouroboros symbol was left at the same scene, bringing it to the attention of the others.
When she was given the option to go to London with Pinkie Pie, Twilight at first declined the offer, saying that she had her mother to take care of. However she changed her mind once she and Nagisa shared the same dream, and as such the same vision by Lugia. While they were visiting England, and getting to know the Phantomhive Manor, Twilight tried to help out Nagisa with his Demon Sense, reassuring him they won't have to stay at the manor.
Sometime later however, Twilight was confronted by Hellgar and she was forced into being his personal spy after he threatened to strangle her with his tail around her neck. As she wanted to not backstab any of her friends however, she instead chose to run away and keep out of Team Harmony's way. She left a note saying she will be doing some training, which she did indeed try to do for a while before Hellgar found her again in another motel. He warned her that it was her job to know about what was going on, and then to tell him. Lucky for her, Grell Sutcliff's arrival made Hellgar retreat, but while Twilight was glad to see him, she had him not tell the others where she was. She refused to go to the Royal Ball as well, which angered Hellgar more for not telling him of it. He warned her that he'll kill everyone if he didn't get anything, which made Twilight finally return to the others. She admitted that she was forced into spying by Hellgar, and helped in getting Hellgar off her back.
She went with them on guard duty for the Queen of England, where Hellgar met with her again. As the fight continued on, she ended up isolated from the others as she tried to get Ciel Phantomhive to come to his senses. When confronted by Hellgar, she made it clear that she wasn't gonna follow him anymore, before she and Ciel were rescued by Sebastian Michaelis. The others thought she was dead until they found her at the manor.
After the Pluton attack on Amestris, she became very distraught when she heard that Nagisa had gone missing, believed to be dead. Twilight refused to believe it, and with Aladdin, went off to go and find him. Their search went on for a few days, as they continued eastward. One night, she and Aladdin were found by Gluttony, but before they could be eaten were saved by Gaara and a fellow accomplice. Twilight tried to follow them, only to find one of Nagisa's bracelets. This got her to believe that Nagisa was with him, and so tracked them down with Aladdin back to Gaara's place. Both she and Aladdin were warned by Gaara himself to get lost, sending them flying away in an attack, but when they tried again later Nagisa himself arrived, much to their joy. She and Aladdin flew back with him the next day.
On their return, Twilight's involvement became more supportive, and when they began to work to alter Nagisa's future visions, she was especially against the final assault when Nagisa planned to disguise himself as Envy. Just before he left, Twilight was actually given a kiss by Nagisa, just to be sure that he had no regrets.
Afterwards, Twilight became a bit distant to Nagisa, unsure fully how to take it. By the end of the new years' festival, Twilight finally admitted that she would've done the same thing if she was in his situation, giving him a kiss back. She and Nagisa decided to take their relationship step by step, and that they didn't have to rush into anything.
When the groups went off to find their demons, Twilight went with Nagisa, Edward Elric and Winry Rockbell to face the Great Tengu. After the encounter, and returning to Tokyo however, she became captured by the Slicer Brothers, and taken to Abaddon.
Nagisa is a very close friend to Twilight, and who she had first given her nickname to outside of her family freely. Their relationship is very close, as Twilight was willing to find him even after the world thought he was dead after the Pluton incident. This developed into love by the end of Season 4.