Reaction was a heavy metal band from Japan that first formed in 1983. They had a passionate cult following, although never really had the chance to completely cross over to the mainstream scene, and ended up disbanding in 1989. In 2006, however, Reaction reunited after nearly two decades apart, and remained active until guitarist Yasu abruptly passed away in December of 2008. The remaining members of Reaction played one more live in April of 2009 in Yasu's honor before disbanding once more.