Because It's The First Time () is a South Korean television series written by Jung Hyun-jung and directed by Lee Jung-hyo.
 It starred Choi Minho, Park So-dam, Kim Min-jae, Jung Yoo-jin, Lee Yi-kyung and Cho Hye-jung.
 It is the first drama produced by OnStyle network and it started airing on October 7, 2015 every Wednesday 23:00 (KST) for eight episodes.
 The series centers around six young people who gather on the rooftop of Tae-oh's house as their hideout.
 They each have their own story.
History of a Salaryman (; lit.
 "Salaryman Cho Han Ji") is a 2012 South Korean television series that aired on SBS from January 2 to March 31, 2012 on Mondays and Tuesdays at 21:55 for 22 episodes.
 Starring Lee Beom-soo, Jung Ryeo-won, Jung Gyu-woon, Hong Soo-hyun, Lee Deok-hwa, and Kim Seo-hyung, the series is a quirky comedy and murder mystery about an ordinary salaryman who finds himself involved with corporate spies and rival pharmaceutical companies.
 It satirizes the historical events during China's Chu–Han Contention (206-202 B.C.) to become a parody of modern office politics.
Shut Up Flower Boy Band ( is a 2012 South Korean television series starring Sung Joon, Jo Bo-ah, L, Jung Eui-chul, Lee Hyun-jae, Yoo Min-kyu, and Kim Min-seok.
 It is a coming-of-age story about a high school rock band dealing with friendship, rivalry, romance and their passion for music.
 The series aired on tvN from January 30 to March 20, 2012 on Mondays and Tuesdays at 23:00 for 16 episodes.
Sunmin (Hangul: 선민, "Katakana": ソンミン, born August 4, 1987) is a South Korean singer who speaks and sings in Korean, Japanese, and English.
 She debuted in 2006, with the single "Keep Holding You," a collaboration with the Japanese R&B singer Toshinobu Kubota.
 Her career was initially focused on the Japanese market, but her work became focused in South Korea from 2009 to 2010.
 She also contributed to original soundtracks of South Korean television series "Master of Study" and "Gloria (2010 TV series)".
 In 2010 to 2011, she was in the main South Korean musical production of "Jekyll & Hyde" as Lucy.
 In 2012 to 2013, she reprised her role as Lucy in the South Korean national tour.
 In spring 2013, Sunmin played Josephine in the South Korean production of "Arsène Lupin", the musical.
Ja Myung Go (; also known as Princess Ja-myung) is a 2009 South Korean television series starring Jung Ryeo-won, Park Min-young and Jung Kyung-ho.
 It aired on SBS from March 9 to July 21, 2009 on Mondays and Tuesdays at 21:55 (KST) for 39 episodes.
Jung Eui-chul (born April 19, 1985) is a South Korean model and actor.
 He made his acting debut in the drama Biscuit Teacher and Star Candy as a student and gained positive response in 2005 and later landed on many supporting roles including the award-winning films such as Five Senses of Eros and popularity based novel film "Do Re Mi Fa So La Ti Do".
 The peak of his career was reached in 2009 as a main role in the award-winning and most popular recognized drama "Boys Over Flowers" which gained international Asia attention.
Boys Over Flowers () is a 2009 South Korean television series starring Lee Min-ho, Ku Hye-sun, Kim Hyun-joong (of SS501), Kim Bum, Kim Joon (of T-Max) and Kim So-eun.
 It aired on KBS2 from January 5 to March 31, 2009 on Mondays and Tuesdays at 22:00 for 25 episodes.
Sweet, Savage Family () is a 2015 South Korean television series starring Jung Joon-ho, Moon Jung-hee, Jung Woong-in and Yoo Sun.
 It aired on MBC on Wednesdays and Thursdays at 22:00 beginning November 18, 2015.
 The series is loosely based on the "Marrying the Mafia" film franchise, which also starred Jung Joon-ho.
City of the Sun () is a 2015 South Korean television series based on the Japanese novel "Bones of Steel" (鉄の骨 , Tetsu no Hone ) by Jun Ikeido.
 Starring Kim Joon, Jung Min, Song Min-jung, Jung Joo-yeon and Kim Sung-kyung, it aired on MBC Dramanet from January 30 to April 7, 2015 for 16 episodes.
The Three Musketeers () is a 2014 South Korean television series starring Jung Yong-hwa, Lee Jin-wook, Yang Dong-geun, Jung Hae-in, and Seo Hyun-jin.
 Loosely based on Alexandre Dumas's novel "The Three Musketeers", the series follows three Joseon-era adventurers who serve Crown Prince Sohyeon as his warrior guards.
 It aired on cable channel tvN from August 17 to November 2, 2014 on Sundays at 21:00 for 12 episodes.

Question: How many episodes does the South Korean television series at which Jung Eui-chul reached the peak of his career have? 
Answer: 25 episodes