documentclass[fontsize=9pt, paper=a5]{scrreprt}
%usepackage{showframe}

usepackage[]{marginnote} % heightadjust deptadjust parboxrestore
renewcommand*{marginfont}{sffamilybfseriesfootnotesize}

usepackage{blindtext}
begin{document}
chapter{First Chapter}
{Huge Huge to highlight the align effect.} marginnote{121}

blindtext
marginnote{122} blindtext
end{document}