Yousuke Yamamoto is a typical underachiever who searches for a reason to live while struggling to accept the death of his friend Noto a year ago. His life changes dramatically one night when he encounters Eri Yukizaki, a beautiful girl concealing her own tragic loss, on the streets. When a giant wielding a chainsaw falls from the sky and engages her in battle, it marks the beginning of Yousuke finally finding his purpose in life.