Sunn O)))'s album Kannon came out in December 2015, and if you were diligently monitoring the band's store, you were probably able to snag a vinyl copy with the bonus 7" flexi. The 7" contained the bonus track "青木ヶ原 // 樹海 (Aokigahara // Jukai)," which is now available for streaming and purchase below via the band's Bandcamp.
Kannon was meant to be a hopeful, light record, so I guess it makes sense to release a song partially named after a famed forest in Japan where people go to commit suicide (Aokigahara) separately. Oh, and wait until the end. Attila Csihar gets extra creepy with the vocals and extraneous noises.