Loner (2008)

Soo-na, a 17 year-old student who lives in a huge mansion with her uncle and grandmother, is driven over the edge after the suicide of her best friend. She locks herself in her room, talks to someone that nobody else can see, and tries to kill herself in front of her family. Her uncle, Se-jin, enlists the help of his fiancée, Yoon-mi, a psychiatrist who specialises in hikikomori. Yoon-mi suspects that Soo-na's condition is related to some hidden family history.