  U(Nc) gauge theory with Nf fundamental scalars admits BPS junctions of domain
walls. When the networks/webs of these walls contain loops, their size moduli
give localized massless modes. We construct Kahler potential of their effective
action. In the large size limit Kahler metric is well approximated by kinetic
energy of walls and junctions, which is understood in terms of tropical
geometry. Kahler potential can be expressed in terms of hypergeometric
functions which are useful to understand small size behavior. Even when the
loop shrinks, the metric is regular with positive curvature. Moduli space of a
single triangle loop has a geometry between a cone and a cigar.
