Secure Unit No. 3, Mirai Kanda, finds herself fighting alone after her comrades Units 1 and 2 go missing. Before her appears not the criminal organization Despair, but a mysterious tentacle monster! Its tentacles radiate crushing force and terror, yet Secure 3 refuses to back down. However, she is suddenly enveloped in a strange light and dragged into a different dimension. There, she is bound to a tentacle cross and assaulted by countless writhing tentacles. The slimy appendages dissolve her combat suit and slither across her beautiful skin, spreading fear. The true identity of this tentacle monster is a demon from another dimension summoned by Despair. Units 1 and 2 were also attacked by this same demon. Can Unit 3 escape this alternate dimension? Will she avenge her fallen comrades? And will this story end in a BAD END?