Question: Who does the double-agent of Hogwarts's headmaster love?

Context articles: Harry Potter (character)
List of Vampire Knight characters
Albus Dumbledore
Harry Potter and the Half-Blood Prince
T. C. Murray
Young Woodley (play)
Harry Potter and the Half-Blood Prince (film)
Severus Snape
Elizabeth Burke

Harry James Potter is the title character and protagonist of J. K. Rowling's "Harry Potter" series.
 The majority of the books' plot covers seven years in the life of the orphan Potter, who, on his eleventh birthday, learns he is a wizard.
 Thus, he attends Hogwarts School of Witchcraft and Wizardry to practise magic under the guidance of the kindly headmaster Albus Dumbledore and other school professors.
 Harry also discovers that he is already famous throughout the novel's magical community, and that his fate is tied with that of Lord Voldemort, the internationally feared Dark Wizard and murderer of his parents, Lily and James.
The "Vampire Knight" manga series and its anime adaptation features a cast of characters created by Matsuri Hino.
 The series takes place at the Cross Academy, where the daughter of the headmaster, Yuki Cross, faces many different types of challenges: from a love triangle between a vampire student named Kaname Kuran and her childhood friend named Zero Kiryu; to many threats on her life and the lives of the people she is trying to protect.
Professor Albus Percival Wulfric Brian Dumbledore is a fictional character in J. K. Rowling's "Harry Potter" series.
 For most of the series, he is the headmaster of the wizarding school Hogwarts.
 As part of his backstory, it is revealed that he is the founder and leader of the Order of the Phoenix, an organisation dedicated to fighting Lord Voldemort.
Harry Potter and the Half-Blood Prince is the sixth and penultimate novel in the "Harry Potter" series, written by British author J. K. Rowling.
 Set during protagonist Harry Potter's sixth year at Hogwarts, the novel explores the past of Harry's nemesis, Lord Voldemort, and Harry's preparations for the final battle against Voldemort alongside his headmaster and mentor Albus Dumbledore.
Thomas Cornelius Murray (17 January 1873 – 7 March 1959) was an Irish dramatist who was closely associated with the Abbey Theatre.
 He was born in Macroom, County Cork, and educated at St Patrick's Teacher Training College in Drumcondra, Dublin.
 He worked as a schoolteacher and in 1900 was appointed headmaster of the national school in Rathduff, Co.
 Cork.
 His first play, "The Wheel of Fortune", was produced by the Little Theatre in Cork in 1909.
 It was revised and renamed "Sovereign Love" in 1913.
 Murray had co-founded the theatre with Daniel Corkery, Con O'Leary and Terence McSwiney.
 In 1915, he moved to Dublin as headmaster of the Model Schools at Inchicore, where he remained until his retirement from teaching in 1932.
Young Woodley is a 1925 play by the British writer John Van Druten.
 It concerns a schoolboy at a top British public school who falls in love with his headmaster's wife and is eventually expelled.
 Because of its negative depiction of public school life and its controversial subject matter the play was originally banned in the United Kingdom and was only staged in 1928.
 However, it was a major success in the United States and Van Druten moved there to work.
 The ban in Britain was eventually lifted and it ran for over 400 performances in the West End making a star of its lead Frank Lawton.
 It was revived at the Finborough Theatre, London, in 2007.
Harry Potter and the Half-Blood Prince is a 2009 British-American fantasy film directed by David Yates and distributed by Warner Bros.
 Pictures.
 It is based on the novel of the same name by J. K. Rowling.
 The film, which is the sixth instalment in the "Harry Potter" film series, was written by Steve Kloves and produced by David Heyman and David Barron.
 The story follows Harry Potter's sixth year at Hogwarts as he receives a mysterious textbook, falls in love, and attempts to retrieve a memory that holds the key to Lord Voldemort's downfall.
Severus Snape is a fictional character in J. K. Rowling's "Harry Potter" series.
 An exceptionally skilful wizard, his coldly sarcastic and controlled exterior conceals deep emotions and anguish.
 A Professor at Hogwarts School of Witchcraft and Wizardry, Snape is hostile to the series' protagonist, Harry, the moment he sets foot in Snape's classroom; this hostility is rooted in Harry's resemblance to Harry's father James, who bullied and harassed Snape during their time at Hogwarts.
 Though philosophically attracted to the Dark Arts and Lord Voldemort's ideology of wizard supremacy, Snape's love for Muggle-born Lily Evans, Harry's mother, eventually compels him to defect from the Death Eaters.
 Snape becomes a double-agent on behalf of Albus Dumbledore and the Order of the Phoenix, and protects Harry throughout the series.
Elizabeth Burke, (fictional) Headmaster at Hogwarts by JK Rowling