Xin (シン) is the grandson of one of Heiyue's elders.
Xin is a boy with black hair and amber eyes. He dresses in an eastern style, with a white changpao with splits along the legs and a red hem, fastened with golden ties. He wears flat gold-embroidered slippers and has an indigo sash around his waist.
Despite his age, Xin is very knowledgeable about the world of business and Heiyue assets. He is idealistic, having a vision of what he wants to achieve and how he should act as a potential successor to the a position of power. Xin is also quite arrogant and assuming that others will do things for his benefit, assuming an air of authority.
After meeting Elie MacDowell by chance, Xin becomes smitten by her, proclaiming her to be the woman of his dreams. He enjoys any chance to spend time with her and is mostly willing to stay on her good side. When it isn't possible, he tells his subordinates to go easier on her, stating that he wouldn't forgive them otherwise.
Xin visits Crossbell to learn about foreign cultures and societies in order to become a successful successor to his grandfather.
Heiyue - Crossbell Branch manager Cao Lee files a request to show Xin around town. He immediately inquires whether Mayor Dieter Crois or performer Ilya Platiere is among the Special Support Section members. Although disappointed, when he learns their name he realizes they were responsible for clearing the Cult Incident, of which he heard from his grandfather.
Then his eyes falls on Elie and proclaims her the woman of his dreams, praising her pearl-grey hair and lovely proportions. Elie, Lloyd Bannings and a character of choice show Xin around the city, bringing him to the places he wished to see.
Xin helps the SSS by exposing a wanted criminal on the train by quizzing them on the Ored state which he has knowledge on and can easily pick apart any holes or lies in their alibi.
He later returns to Calvard by train.
Xin and Lau are looking after the Crossbell branch whilst Cao negotiates with the Governor General. Xin enlists the new Class VII and Rean Schwarzer to help retrieve a briefcase containing important documents and letters pertaining to those of the SSS or their allies trapped by Operation Birdcage. He states he has asked the party to do this mainly for 'Her' (Elie). Xin takes a great interest in Emma Millstein and Alisa Reinford as well, ordering Lau to get the best tea.
Xin is first seen with Cao Lee and Lau, worried about the potential outbreak of war. He refuses to leave Crossbell as he does not want to abandon Elie.
He later accompanies the two to Geofront's Block X where he encounters Class VII. Elie arrives with Estelle Bright to save the group from their archaisms. He was happy to see Elie again, indirectly ordering Cao to go easy or he wouldn't forgive him for harming her. He later has a chance to see her again after Cao once again gives his support and changes sides.
Xin is mentioned as having left Crossbell prior to the takeover by Supreme Leader Rufus Albarea. After he heard about what had happened, he felt it was his duty to return and offer his apologies for how Heiyue was used. Cao had moved him for his own safety, stating that he was merely evaluating the Supreme Leader's strength. Xin promises to protect Elie's smile and says he will advise his grandfather, father and sister to assist as well, and through them he knows how to have influence in the Republic.