  The problem of elementarity of electric charge is investigated. It is known
that possible proton decay is caused by $X$ and $Y$ bosons which are
characteristic in GUTs. The charge structure of GUTs is, however, not simple,
and the five types of charge units appear. We investigate the problem of
elementarity in taking into account of the simplest model of the charge
structure known as the rishon model, where the charge units are known as 1/3
($T$) and 0 ($V$). In order to approach to sub-structure together with the
problem of simplicity of charge structure, possible rearrangements of rishons
are investigated on the basis of color and hypercolor confinement condition.
Further, possible existence of the simplest electroweak sub-structure is
discussed. Our model predicts possible proton decay mode, in which $X$ and $Y$
bosons are not concerned.
