  The coexistence of edge states and skin effects provides the topologically
protected localized states at the corners of two-dimensional systems. In this
paper, we realize such corner states in the two-dimensional
Su-Schrieffer-Heeger model with the nonreciprocal hoppings. For the
characterization of the real line gap topology, we introduce the $\mathbb{Z}_4$
Berry phase protected by generalized four-fold rotational symmetry. From the
physical picture of the adiabatic connection, we find that the value of the
$\mathbb{Z}_4$ Berry phase predicts the position of edge states. Additionally,
by using the winding number, we characterize the point gap topology of the edge
spectra. From the results of these characterizations by the first-order
topological invariants, we find that the pair of values of the $\mathbb{Z}_4$
Berry phase and the winding number yields the position of the topologically
protected localized states.
