Just Friends?

Min Soo is on leave from the military and visits his boyfriend Seok Yi. While having fun out on the town, they run into Min Soo's mother! When Min Soo's mother asks about their relationship, Seok Yi replies "... just friends." Making things more complicated, Min Soo's mother ends up sleeping with them that night!
(Source: AsianWiki)
~~ 29 minute film duration, plus an additional 25 minutes of behind the scenes footage on some versions.