KNIFE+HEART isn't the first work of art to combine the specter of the AIDS epidemic, the sex positivity of the gay liberation movement (which came to a crashing halt with the emergence of AIDS), and the conventions of horror/thriller/slasher films. In poetry form, Kevin Killian's 1997 ARGENTO SERIES fused the brightly colored blood splatter of SUSPIRIA with the inexplicable death toll of HIV. Probably my favorite of all such works, however, is Alain Guiraudie's 2014 film STRANGER BY THE LAKE, which yearns for the titillation of casual sex even as it constantly exudes the threatening possibilities inherent in such encounters in a way that's truly unsettling.
KNIFE+HEART isn't about AIDS, per se, but it does pile on a nicely textured layer of meanings about the interlocking nature of the sex and the death drive. The violent impulses that underlie S&M fantasies; the death of the ego that makes dance floors, drug trips, and uninhibited sexual encounters equally ecstatic; the orgasmic peak that led English Renaissance poets to use "die" as a metaphoric synonym for "climax"; the "death" of the presumed-straight child that occurs whenever a queer adolescent or adult comes out of the closet and must then sometimes abandon past expectations, past claims to identity, and links to old family and friends; the loss a parent might feel when a child leaves for a safer queer space like the city; the loss of one's individuality when entering into a committed partnership with another person; the godlike control over life and death that lies in both the hands of the artist and the medium of photography, which captures and preserves moments in time; and the literal violence and murder perpetrated against not only queer and trans people but also sex workers in general--KNIFE+HEART is about all of this, I think, and probably a lot more, including things perhaps too personal for a viewer to decipher.
KNIFE+HEART carries a heavy load of theoretical possibilities, but it never comes across as pretentious or overladen. Rather, it's consistently engaging, with campy excesses of giallo bloodshed, a proliferation of cute boys, a pulsing soundtrack by M83, and bits of both levity and realism that make it moving even though it is essentially, like the best of Argento, utterly ridiculous and implausible. It may not have quite the same high style that peak Argento had, but it definitely has a lot more substance.