  Tri-direct CP symmetry is an economical neutrino model building paradigm, and
it allows to describe neutrino masses, mixing angles and CP violation phases in
terms of four free parameters. Viability of a class of tri-direct CP models is
examined with a comprehensive simulation of current and future neutrino
oscillation experiments. Two benchmark models as well as the full parameter
space are carefully scanned, and the parameter degeneracy problem is observed
from the constraint of one group of neutrino oscillation experiments.
Complementary roles from the accelerator neutrino experiments (e.g., T2HK and
DUNE) and reactor neutrino experiments (e.g., JUNO) are crucial to break the
degeneracy and nail down fundamental neutrino mixing parameters of the
underlying theory.
