Hyeokjae Kim was born in 1998 in Jeju Island (Jeju-do), South Korea. When he was a teenager, he began music by making hip-hop beats and playing guitar in several rock bands. Then, at the age of 16, after he was first exposed to the music of Stravinsky and Ligeti and taught himself composition. He completed bachelor degree in composition with distinction (mit Auszeichnung) at the University of Music and Performing Arts Graz with Prof. Klaus Lang.
His music has been performed by numerous performers and conductors including Ensemble Intercontemporain, Klangforum Wien, International Ensemble Modern Academy, Schallfeld Ensemble, Divertimento Ensemble, Ensemble Court-Circuit, Ensemble Nostri Temporis, S201, Ensemble TIMF, Ensemble blank, Emilio Pomàrico, Sandro Gorli, Claire Levacher, Jean Deroyer, Jaehyuck Choi etc., at numerous festivals and workshops including Lucerne Festival (Switzerland) IRCAM ManiFeste (France), Festival de Royaumont (France), IDEA Workshop for Young Composers (Italy), Como Contemporary Festival (Italy), OutHear New Music Week (Greece), Contrasts Contemporary Music Festival (Ukraine), MicroFest Prag (Czech), Daegu International Contemporary Music Festival (South Korea) etc.
He also has won the 3rd prize at the Eduardas Balsys International Composition Competition (Lithuania). And he was selected as a finalist at EarPlay International Composition Competition (USA), Ensemble NeuverBand Basel International Construct-Radiatie Composition Competition (Switzerland), and Appassionate Ensemble International Composition Compeititon (Italy).

His music is published by Universal Edition.
He doubts the ideology of novelty in contemporary music, and does not pursue new sounds or new aesthetics. He just concentrates on writing the notes he needs to write every moment.