In the novel, Swin is portrayed as a 13-year-old boy and the partner of Nadia. He entered the Organisation at the age of 7 and graduated from Training School at the age of 10. For the three years since his graduation, he's been working as an assassin under the alias of Three of Swords.
His previous partner was Ace, a boy on year his age. Ace's failed attempt to leave the Organisation cost him his life. Ace's death continues to haunt Swin.
Swin excels at close combat, wielding a longsword and shortsword that can be combined into a greatsword.