newenvironment{overview}%
  {onecolumnvtop to 0ptbgroupchapter*{Overview}begin{multicols}{2}}%
  {end{multicols}vssegrouphfilltwocolumn}

documentclass[b5paper,twoside]{scrbook}
usepackage{adjustbox}
usepackage{multicol}

usepackage{lipsum}

newlength{innerMargin}
setlength{innerMargin}{3cm}
usepackage[inner=innerMargin]{geometry}

makeatletter
newcommand{twopager}[1]{%
    cleardoubleevenstandardpage
    adjustbox{trim=0 0 {innerMargin+columnwidth} 0, clip}{%
    begin{minipage}{2textwidth}
    addchap{Title}
    setlength{columnsep}{2innerMargin}
    begin{multicols}{2}
    #1
    end{multicols}
    end{minipage}
    }%
newpage
    adjustbox{trim={innerMargin+columnwidth} 0 0 0, clip}{%
    begin{minipage}{2textwidth}
    addchap{Title}
    setlength{columnsep}{2innerMargin}
    begin{multicols}{2}
    #1
    end{multicols}
    end{minipage}
}%
cleardoublepage
}
makeatother

begin{document}
lipsum

twopager{lipsum[1-5]}

lipsum
end{document}