  We have shown in a previous paper that two identical detectors with each
fiducial mass of 0.27 megaton water, one in Kamioka and the other in Korea,
which receive the (anti-) muon neutrino beam of 4 MW power from J-PARC facility
have potential of determining the neutrino mass hierarchy and discovering CP
violation by resolving the degeneracies associated with them. In this paper, we
point out that the same setting has capability of resolving the \theta_{23}
octant degeneracy in region where sin^2 2\theta_{23} \lsim 0.97 at 2 standard
deviation confidence level even for very small values of \theta_{13}.
Altogether, it is demonstrated that one can solve all the eight-fold neutrino
parameter degeneracies in situ by using the Tokai-to-Kamioka-Korea setting if
\theta_{13} is within reach by the next generation superbeam experiments. We
also prove the property called ``decoupling between the degeneracies'', which
is valid to first order in perturbation theory of the earth matter effect, that
guarantees approximate independence between analyses to solve any one of the
three different type of degeneracies.
