Question: The confucian academy, Dosan Seowan, located in the East Asian country bordered by China to the northwest and Russia to the northeast, was founded by two prominant Confucian scholars, one being known as Yi Yulgok. What was the "pen" name of the other founding scholar?
Context: The Gosan Seowon is a "seowon" located in the village of Gwangeum-ri, Namhu-myeon of Andong, North Gyeongsang Province, South Korea.  Seowon is a type of local academy during the Joseon Dynasty (1392–1897).  It was first established by local Confucian scholars in 1789, the 13th year of King Jeongjo's reign, to commemorate the scholarly achievement and virtue of the Confucian scholar Yi Sang-jeong (李象靖 1711-1781). Sungyang Hall is a fourteenth-century Confucian academy located on the side of Mt. Janam in Kaesong, North Korea.  The hall was constructed in the late fourteenth century for the home of the famously loyal statesman and Confucian scholar Jong Mong-ju, whose 1392 assassination by the agents of the later Taejo of Joseon marked the end of the Koryo dynasty.  In 1573, the building was transformed into a Confucian academy. The Oksan Seowon is a "seowon" (a private educational institution in Korea which functioned as both an academy and a Confucian shrine) located at Oksan-ri, Angang-eup in the city of Gyeongju, North Gyeongsang Province, South Korea.  Seowon is a type of local academy during the Joseon Dynasty (1392–1897).  It was established by Yi Je-min, (李齊閔), the minister of Gyeongju and local Confucian scholars in 1572, the fifth year of King Seonjo's reign, to commemorate the scholarly achievement and virtue of Confucian scholar and politician Yi Eon-jeok (1491–1553). The Byeongsan Seowon is a "seowon" located in the neighborhood of Byeongsan-dong, Yecheon-myeon in the city of Andong, North Gyeongsang Province, South Korea.  Seowon is a type of local academy during the Joseon Dynasty (1392–1897).  It was first established as Jondeosa (尊德祠) by local Confucian scholars especially Jeong Gyeong-se (鄭經世) in 1613, the fifth year of King Gwanghaegung's reign, to commemorate the scholarly achievement and virtue of the notable Confucian scholar and politician Yu Seong-ryong.  The predecessor of the seowon was Pungak Seodang (淵岳書堂) which was an educational institution located in Pungsan to teach the Pungsan Yu clan during the Goryeo period.  Yu Seong-ryong moved the seodang to the current place in 1572. Korea is a historic country in East Asia, since 1945 divided into two distinct sovereign states: North Korea (officially the "Democratic People's Republic of Korea") and South Korea (officially the "Republic of Korea").  Located on the Korean Peninsula, Korea is bordered by China to the northwest and Russia to the northeast.  It is separated from Japan to the east by the Korea Strait and the Sea of Japan (East Sea). Yi I (Hangul: 이이 ; Hanja: 李珥 , December 26, 1536 – February 27, 1584) was one of the two most prominent Korean Confucian scholars of the Joseon Dynasty, the other being his older contemporary, Yi Hwang (Toegye).  Yi I is often referred to by his pen name Yulgok ("Chestnut valley").  He is not only known as a scholar but also as a revered politician and reformer.  He was academical successor of Jo Gwang-jo. The Holy Confucian Church or Holy Church of Confucius (孔圣会 "Kǒngshènghuì") or Holy Confucian Church of China (中华孔圣会 "Zhōnghuá Kǒngshènghuì") is a body formed of many local Confucian churches or halls (孔圣堂 "Kǒngshèngtáng") in China.  The grassroots movement was initiated by Zhou Beichen, a disciple of the Confucian philosopher Jiang Qing, who founded the first holy church in Shenzhen in 2009.  The aim of the movement was to develop a network of local Confucian churches throughout the country, eventually unifying into a national body and becoming the state religion of China.  The Holy Confucian Church has received support from the Confucian Academy of Hong Kong, although it has developed independently from the latter. Yi Hwang (1501–1570) is one of the two most prominent Korean Confucian scholars of the Joseon Dynasty, the other being his younger contemporary Yi I (Yulgok).  A key figure of the Neo-Confucian literati, he established the Yeongnam School and set up the Dosan Seowon, a private Confucian academy.  Yi Hwang is often referred to by his pen name Toegye ("Retreating Creek").  His courtesy name was Gyeongho. Jeong Gu(korean:정구, hanja:鄭逑, 1543–1620) was Korean philosopher, politician, historian and writer, Confucian scholars of the Joseon Dynastys. learn from Yi Hwang and Cho Shik.  a key figure of the Neo-Confucian literati, he established the Yeongnam School and set up the Baikmaewon(백매원, 百梅園), a private Confucian academy.  his nickname was Hangang(한강, 寒岡)·Hoiyunyain(회연야인, 檜淵野人), courtesy name was Dogah(도가, 道可), Gabo(가보, 可父). Dosan Seowon (alternatively, Tosansowon) was established in 1574 in what is present day Andong, South Korea, in memory of and four years after the death of Korean Confucian scholar Yi Hwang by some of his disciples and other Korean Confucian authorities.  Yi Hwang had retired to the location in 1549 and begun construction on the facility, a private Korean Confucian academy offering instruction in the classics and honouring the sages with regular memorial rites.
Answer: Yi Hwang is often referred to by his pen name Toegye ("Retreating Creek").