Question: Kai appeared in a Korena production of a musical based on a book by Gaston Leroux released in what year?

Context paragraphs:
Phantom of the Opera (1943 film): Phantom of the Opera is a 1943 musical horror film directed by Arthur Lubin and produced and distributed by Universal Pictures.  The film stars Nelson Eddy, Susanna Foster, and Claude Rains, and was filmed in Technicolor.  The original music score was composed by Edward Ward.  The film is loosely based on the novel "The Phantom of the Opera" by Gaston Leroux and its 1925 film adaptation starring Lon Chaney.

Adaptations of The Phantom of the Opera: There have been many literary and dramatic works based on Gaston Leroux's novel "The Phantom of the Opera," ranging from stage musicals to films to children's books.  Some well known stage and screen adaptations of the novel are the 1925 film and the Andrew Lloyd Webber musical (see "The Phantom of the Opera (1986 musical)"); Susan Kay's 1990 "Phantom" is one of the best known novels and includes in-depth study of the title character's life and experiences.

Phantom (musical): Phantom is a musical with music and lyrics by Maury Yeston and a book by Arthur Kopit.  Based on Gaston Leroux's 1910 novel "The Phantom of the Opera", the musical was first presented in Houston, Texas in 1991.

The Phantom of the Opera (1986 musical): The Phantom of the Opera is a musical with music by Andrew Lloyd Webber and lyrics by Charles Hart and Richard Stilgoe.  Lloyd Webber and Stilgoe also wrote the musical's book together.  Based on the French novel "Le Fantôme de l'Opéra" by Gaston Leroux, its central plot revolves around a beautiful soprano, Christine Daaé, who becomes the obsession of a mysterious, disfigured musical genius living in the subterranean labyrinth beneath the Opera Garnier.

The Phantom of the Opera (2004 film): The Phantom of the Opera is a 2004 British-American musical drama film based on Andrew Lloyd Webber's 1986 musical of the same name, which in turn is based on the French novel "Le Fantôme de l'Opéra" by Gaston Leroux.  It was produced and co-written by Lloyd Webber and directed by Joel Schumacher.  It stars Gerard Butler in the title role, Emmy Rossum as Christine Daaé, Patrick Wilson as Raoul, Miranda Richardson as Madame Giry, Minnie Driver as Carlotta Giudicelli, and Jennifer Ellison as Meg Giry.

The Phantom of the Opera: The Phantom of the Opera (French: Le Fantôme de l'Opéra) is a novel by French writer Gaston Leroux.  It was first published as a serialisation in "Le Gaulois" from 23 September 1909, to 8 January 1910.  It was published in volume form in late March 1910 by Pierre Lafitte.  The novel is partly inspired by historical events at the Paris Opera during the nineteenth century and an apocryphal tale concerning the use of a former ballet pupil's skeleton in Carl Maria von Weber's 1841 production of "Der Freischütz".  It has been successfully adapted into various stage and film adaptations, most notable of which are the 1925 film depiction featuring Lon Chaney, and Andrew Lloyd Webber's 1986 musical.

Phantom of the Opera (1976 musical): Phantom of the Opera is a 1976 musical with book and lyrics by Ken Hill.  It is the first musical adaptation of the novel "The Phantom of the Opera" by Gaston Leroux, about the hideously disfigured Phantom's amorous obsession with the magnificent, naïve singer, Christine.  Hill wrote the original English lyrics to the music of Verdi, Gounod, Offenbach, Mozart, Weber, Donizetti, and Boito.

Kai (musician, born 1981): Jung Ki-Yeol (born December 5, 1981), known professionally as Kai, is a South Korean singer and musical theatre actor.  He is best known in musical theatre, and has starred in Korean productions of "A Tale of Two Cities", "The Three Musketeers" and "Phantom".

The Phantom of the Opera (miniseries): The Phantom of the Opera is a 1990 NBC two-part drama television miniseries directed by Tony Richardson and stars Charles Dance in the title role.  It is adapted from Arthur Kopit's book for his then-unproduced stage musical "Phantom", which is based loosely on Gaston Leroux's novel.

A Monster in Paris: A Monster in Paris (French: "Un monstre à Paris" ) is a 2011 French 3D computer-animated musical comedy science fantasy adventure film directed by Bibo Bergeron, produced by Luc Besson, written by Stéphane Kazandjian, distributed by EuropaCorp Distribution, features the voices of Sean Lennon, Vanessa Paradis, Adam Goldberg, Danny Huston, Madeline Zima, Matthew Géczy, Jay Harrington, Catherine O'Hara, and Bob Balaban and based on a story he wrote.  Some aspects of the film are (very loosely) based on Gaston Leroux's novel "The Phantom of the Opera".  It was released on 12 October 2011.  It was also produced by Bibo Films, France 3 Cinéma, Walking The Dog, uFilm, uFund, Canal+, France Télévisions, CinéCinéma, Le Tax Shelter du Gouvernement Fédéral de Belgique and Umedia.  Its music was composed by Matthieu Chedid, Sean Lennon and Patrice Renson.  It was edited by Pascal Chevé and Nicolas Stretta.

Supporting paragraphs: Kai (musician, born 1981) Phantom (musical)
Answer: 1910