Sundome 4: The Final 2009 on netflix

The boyfriend of a Japanese high school girl comes to know about the older man his girl is also seeing. The older man pays for a sushi meal for the high school boy. The boy does not want to accept and wants to return the money so begins working part-time at a karaoke bar to earn income. The girlfriend asks him to come over to her place one day. They spend time together, he goes out to buy drinks and when he returns she has disappeared. There is blood in her room.