Component of the SWM histone demethylase complex that specifically demethylates H3K9me2, a specific tag for epigenetic transcriptional activation, thereby acting as a corepressor. Has a role in regulating heterochromatin propagation and euchromatic transcription. Component of the SWM histone demethylase complex composed of at least lsd1, lsd2, phf1 and phf2.