The big question, of course, is just why has the hanryu boom been so successful? Mutual profit, timing and quality seem to be the answers. The entertainment industries in both countries quickly recognized the lucrative potential of the pop culture exchanges, and have actively promoted them. It would be difficult to even try to estimate the reverberating economic impact that all the hanryu spin-off industries, from publications and tourism to language study and licensing, have produced.

The cross-cultural entertainment world influences are now so great, it's hard to imagine that this all took off just four years ago with one memorable TV drama -- "Winter Sonata," starring Bae Yong-joon and Choi Ji-woo. NHK, the national public broadcaster, decided to try it Saturdays at 11:10 p.m. in a time slot usually reserved for U.S. and British fare. Like all the Korean dramas shown on NHK since, it was broadcast with Japanese voiceovers. Japanese TV viewers, especially middle-aged women, quickly were carried away by the sensitive love story. Soon, glasses and wool scarves were fashion statements. Yong-sama, as he affectionately became known, was being carved in ice at the Sapporo Snow Festival, and tours to the filming locations became all the rage. NHK quickly followed up with "Beautiful Days," "All In," "Spring Waltz," and the historical dramas "Damo" and the very popular "Daejanggum," which NHK also later ran in animated form for the kids. Asian dramas have occupied the Saturday 11 p.m. time slot ever since. Those desperate for "Desperate Housewives or "ER" now have to wait until 1 a.m. As an added bonus for those who stay up even later, "Himawari" with Lee Byung-hun airs at 1:50 a.m.

The historical dramas and lighter Korean romantic comedies broadcast on satellite TV and available for sale or rental on DVD have insured that hanryu fans now include both sexes and all age groups. The appetite of the most dedicated fans has become insatiable, and has stimulated interest in Korean movies, music, musicals and tourism.

A Hanryu Cinema Festival featuring 14 films, mostly starring actors who are familiar to Japanese TV fans, is running again this year in Tokyo and Osaka from March to May. (Check http://www.cinemart.co.jp/han-fes2008). The spring 2008 travel brochures advertising Korean destinations are offering tickets to the popular musicals "Nanta (Cooking)" and "Jump," besides promoting all-in sights on Jeju, "Daejanggum" locales and dining experiences and, for the die-hard Bae Yong-joon fans, a Yong-sama "mo ichido" (once again) tour that even includes his college campus. JTB also sponsored special tours to the open sets used in "Jumong" in February and March. And the list of Korean actors and musicians coming to Japan for concert tours, fan meetings, dinner shows or to release albums here grows longer by the day. March promises Big Bang concerts and the release of the first SG "Wanna Be + Japan" album.

The desire for ever more information on the activities of Korean entertainers has led many big-name Tokyo publishers to issue an impressive array of hanryu magazines, directories and the glossy photo-heavy, magazine-style books known in Japan as "mooks." Those who want even quicker access to the Korean entertainment scene news can get up-to-the-minute bulletins on their cell phones.

With all the dramas and information now available, Japanese hanryu enthusiasts are becoming increasingly knowledgeable. The latest directory of Korean stars includes the profiles of 780 actors, directors and scriptwriters. Truly dedicated hanryu fans can even test themselves on how much trivia they have amassed.

"Kentei" (proficiency tests) in all sorts of subjects, from languages to local history, are popular in Japan, and the first introductory-level "hanryu kente" (a project done in conjunction with JTB) is currently underway. Those who pay for and successfully complete the test on-line will receive certificates of proficiency and be eligible for special TV tours to Korea. An intermediate-level exam is already planned for May. Those who think they have watched enough Korean dramas to qualify may want to try the mini-test at http://www.k-x.jp, with sample multiple-choice questions like: Amnesia is a recurring theme in Korean dramas. Select the drama which did not deal with this theme.

Few fans take their fascination to this level, but even occasional and casual TV viewers will recognize the names of the stars of those first few NHK series -- Bae Yong-joon, Choi Ji-woo, Lee Byung-hun, Ryu Shi-won and Lee Young-ae -- and their works -- "Winter Sonata," "Daejanggum," "Stairway to Heaven," "Beautiful Days," and "Hotelier" -- which top a list of the most popular Korean dramas in Japan, according to a survey of 1,600 Japanese, mainly women in their 30s, done in 2007 by the TV Asahi program SMAStation. Hosted by SMAP's Shingo Katori, the program unfortunately has had to compete with these dramas in the Saturday, 11 p.m. time slot. And even Japanese TV scripts have begun to recognize the hanryu presence as a part of the modern 21st century Japanese lifestyle. In the recent Japanese TV series "Hatachi no Koibito," the heroine's colleague is a devoted Lee Byung-hun fan who reads hanryu magazines on her breaks, and rushes off from work to attend his fan meetings.

This brings us to the second important aspect of the hanryu success: the timing was right. Had the Korean Wave arrived five or 10 years sooner, when Japan's own TV dramas were at their peak and bringing in average ratings of over 30 percent, the hanryu boom might have faced a more difficult challenge. But, for the last few years, Japanese dramas have been weathering a considerable slump. Although two dozen series are launched each quarter, it has become extremely difficult for most to get anywhere near 15 percent ratings, and few top that figure. Only dramas starring SMAP's Takuya Kimura have been consistently capable of climbing up over the 30 percent mark in the new century. Irritating or inconclusive endings, predictable dialogue and a trend away from serious romances have discouraged viewers, and created a vacuum that the quality Korean products have very conveniently filled. Serious drama fans have taken refuge in the parallel hanryu world with its overall high quality, straightforward and sincere style, freer expression of emotions and romantic leading men.

Hanryu dramas might even be able to help enliven the Japanese prime time lineup, now heavy with variety shows and trivia quizzes, if given a chance, but foreign TV series have been unable to significantly break through into the 8-11 p.m. market. Since 1990, I can recall only one foreign drama that was able to crack that barrier and be welcomed into the Japanese prime time schedule -- "The X Files" in 1995.

Still, the hanryu phenomenon has become secure enough in its niche that it has been able to make some dents in the barrier in two ways: Japanese remakes of Korean hits, and appearances by Korean stars in Japanese dramas. In 2006, Tokio's Tomoya Nagase starred in a successful remake of "My Boss, My Hero," the Korean comedy about a gangster who goes back to high school that was among the top ten-rated Japanese TV dramas that year. A Japanese remake of "Hotelier" was less successful, even though it featured a cameo guest appearance by Bae Yong-joon. SMAP's Tsuyoshi Kusanagi and actress Reina Tanaka will appear in "Ryokiteki na Kanojo," a remake of the 2001 hit Korean movie "My Sassy Girl" beginning in April, 2008.

Korean stars who have tried acting in Japanese dramas have faced a bigger challenge. Choi Ji-woo starred in "Rondo" in 2006 and Ryu Shi-won co-starred with Japan's top actress Yukie Nakama in "Joshi Deka (Lady Detective)" in 2007, but the latter reached only 54th place in the year's drama rankings. Both series met with only moderate success, in part because the Korean stars were not given ample opportunity to display their talents.

While hanryu fans in Japan might idolize the Korean stars, and rush to their fan club meetings, what they are really buying is the whole Korean drama package -- the excellent camera work, the passion, the direction, the perkier dialogue and plots, the detail regarding fashion, and the beautiful background music that make them a distinctly Korean commodity. Thus, Korean stars might want to think twice before accepting roles in Japanese series.

Korean actors who want to try their hand at Japanese dramas may find it educational, but it is also a career choice fraught with peril. Their popularity on the archipelago may be more secure if they continue to star in domestic Korean dramas with export value, and only pop across the sea for periodic personal appearance tours, rather than getting caught up in the slumping continuing-drama-series crunch in Japan.

Although Ryu Shi-won's week-long guest appearance on the 2007 NHK morning serial "DonDon Hare" significantly helped spike ratings for that series, just look at what he faced in one romantic scene with Yukie Nakama in "Joshi Deka:" In the scene where she is so distraught that she hasn't eaten all day, what does the script call for -- a kiss, a hug, empathy, sympathy? Not even some concerned and caring Korean drama-style wrist yanking (which makes one wonder if repeated strain wrist injuries are an occupational hazard for Korean actresses who have to rehearse scenes like that all day).

No, Ryu Shi-won has to tell her to close her eyes. Then he leans over and pinches her nose while shoving a morsel of food into her mouth. Ridiculously unromantic and a waste of his talents. And the Japanese networks wonder why their drama ratings are plummeting, while the public craves serious romances. As long as Korean dramas continue to fill this void, the hanryu boom should continue to be a lucrative niche industry in Japan.

The next bounce will no doubt come from "Taewangsasingi," starring Bae Yong-joon. Already running on NHK's satellite channel, it will be broadcast in NHK's lucky Saturday 11:10 p.m. terrestrial time slot from April 5. Japanese actor Masato Hagiwara, whose own career got a boost when he did the Japanese voiceovers for Yong-sama in "Winter Sonata," will be back to give voice to the hero again.

For now, it looks like the hanryu TV boom is here to stay and will continue to bring the peninsula and the archipelago closer together through couch-potato diplomacy.

By Kathleen Morikawa