I need help finding film for a psych project.?

Does it necessarily need to be live action? If not, then look into anime, as there is a lot (both recent and old). Most easy to highlight is the blatant title "I Love My Younger Sister" (Boku wa Imōto ni Koi o Suru). Its manga was published in 2003-2005, and the anime adaptation was released in 2005. It was also popular enough that it was adapted again into live action in 2007, so in that regard it should still meet your requirements. Though it would be available in japanese-language only (finding it with subtitles is possible). I'd say it takes a very good approach to the topic.