When the members of hard rock band Ningen Isu left the stage at Ozzfest Japan in 2013, they thought that was it for their Ozzfest experience. Little did the "Japanese Black Sabbath" know, Ozzy Osbourne himself would soon be calling them back for an encore.

"When the organizers asked us to play again in 2015, we knew that the dream wasn't over yet," says guitarist Shinji Wajima. "Last year was when I knew that we were in a good place as a band."

Playing at Ozzfest Japan was just one of the milestones for Wajima and his bandmates, bassist Kenichi Suzuki and drummer Nobu Nakajima (all three handle singing duties), in 2015. After celebrating its 25th anniversary with the release of a two-disc best-of compilation and a return to Shibuya Public Hall for the first time in two decades, the band found the rest of the year fruitful, penning an instrumental soundtrack for the TBS/JBS television drama "JK wa Yuki Onna," releasing a collaboration single with contemporaries Kinniku Shojo Tai, and contributing to a compilation soundtrack for the anime "Ninja Slayer." The band also performed with a slew of other bands, including heavy metal veterans Doom, instrumental prog-rockers Hachijyuhakkasho Jyunrei and internationally acclaimed drone-noise rockers Boris.