A spring rugby tournament (2010년도 전국춘계럭비리그전) opened on Monday in Gangjin county, with Daegu's Sangwon High School (대구상원고등학교) beating Gyeongsan's eponymous high school (경산고등학교) 12-8.
Seven middle school and fourteen high school teams will play from the 15th through the 27th, the A group for the university level will play from April 3rd through 11th, and the B group goes from March 27th through the 31st. This article says Cheongju Boys' Middle School and Chungbuk High School were last year's winners. The middle school, high school, and the A group play in Gangjin, while group B plays in Seoul (서울럭비구장). The Korea Rugby Union website doesn't provide information about these matches, but if you'd like to watch a couple you might try emailing the address given on the English-language pop-up (email@example.com) for details.
But given the difficulty I've had trying to track down the most basic information, I think maybe it's supposed to be a secret. The article says the matches in Gangjin take place at the 공설운동장. That's not really the name of the public fields out at 강진종합경기장, but if I had to take a guess I'd say the matches are there, on fields built a couple years ago next to a large facility about a 25 minute walk northeast of the bus terminal in Gangjin-eup, the county seat (map in Korean here). Gangjin is roughly two hours south of Gwangju by bus.