masawada

\documentclass[a4j, 10pt, dvipdfmx]{jsarticle}
\usepackage[dvipdfmx]{graphicx}
\usepackage{tikz}
\usetikzlibrary{matrix,calc}

% ref: http://tex.stackexchange.com/questions/36798/remove-vertical-lines-for-table/36879#36879

%internal group
%#1-space between node and grouping line. Default=0
%#2-top left node