  Recently, complex phase transitions accompanied by the rotational symmetry
breaking have been discovered experimentally in cuprate superconductors. To
find the realized order parameters, we study various charge susceptibilities in
an unbiased way, by applying the functional-renormalization-group method to the
realistic $d$-$p$ Hubbard model. Without assuming the wavevector of the order
parameter, we reveal that the most dominant instability is the uniform ($q =
0$) charge modulation on the $p_x$ and $p_y$ orbitals, which possesses the
d-symmetry. This uniform nematic order triggers another nematic p-orbital
density wave along the axial (Cu-Cu) direction at $Q_a = (\pi/2,0)$. It is
predicted that uniform nematic order is driven by the spin fluctuations in the
pseudogap region, and another nematic density-wave order at $q = Q_a$ is
triggered by the uniform order. The predicted multistage nematic transitions
are caused by the Aslamazov-Larkin-type fluctuation-exchange processes.
