diff --git a/phono3py/interface/wien2k.py b/phono3py/interface/wien2k.py
index c8dbf955..a823fb3d 100644
--- a/phono3py/interface/wien2k.py
+++ b/phono3py/interface/wien2k.py
@@ -34,7 +34,7 @@
 # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
 
-from phono3py.phonon3.dataset import get_displacements_fc3
+from phono3py.phonon3.dataset import get_displacements_and_forces_fc3
 
 
 def get_fc3_calc_dataset_wien2k(
@@ -48,8 +48,7 @@ def get_fc3_calc_dataset_wien2k(
     """Read Wien2k output files and parse force sets."""
     from phonopy.interface.wien2k import parse_set_of_forces
 
-    #    disps, _ = get_displacements_and_forces_fc3(disp_dataset)
-    disps = get_displacements_fc3(disp_dataset)
+    disps, _ = get_displacements_and_forces_fc3(disp_dataset)
     force_sets = parse_set_of_forces(
         disps,
         force_filenames,
diff --git a/phono3py/phonon3/dataset.py b/phono3py/phonon3/dataset.py
index ad2a4122..d65aea92 100644
--- a/phono3py/phonon3/dataset.py
+++ b/phono3py/phonon3/dataset.py
@@ -39,7 +39,9 @@
 import numpy as np
 
 
-def get_displacements_and_forces_fc3(disp_dataset):
+def get_displacements_and_forces_fc3(
+    disp_dataset: dict,
+) -> tuple[np.ndarray, Optional[np.ndarray]]:
     """Return displacements and forces from disp_dataset.
 
     Note
@@ -71,10 +73,13 @@ def get_displacements_and_forces_fc3(disp_dataset):
         forces = np.zeros_like(displacements)
         indices = []
         count = 0
+        forces_count = 0
         for disp1 in disp_dataset["first_atoms"]:
             indices.append(count)
             displacements[count, disp1["number"]] = disp1["displacement"]
-            forces[count] = disp1["forces"]
+            if "forces" in disp1:
+                forces_count += 1
+                forces[count] = disp1["forces"]
             count += 1
 
         for disp1 in disp_dataset["first_atoms"]:
@@ -86,69 +91,26 @@ def get_displacements_and_forces_fc3(disp_dataset):
                     indices.append(count)
                 displacements[count, disp1["number"]] = disp1["displacement"]
                 displacements[count, disp2["number"]] = disp2["displacement"]
-                forces[count] = disp2["forces"]
+                if "forces" in disp2:
+                    forces_count += 1
+                    forces[count] = disp2["forces"]
                 count += 1
-        return (
-            np.array(displacements[indices], dtype="double", order="C"),
-            np.array(forces[indices], dtype="double", order="C"),
-        )
-    elif "forces" in disp_dataset and "displacements" in disp_dataset:
-        return disp_dataset["displacements"], disp_dataset["forces"]
-    else:
-        raise RuntimeError("disp_dataset doesn't contain correct information.")
-
-
-def get_displacements_fc3(disp_dataset):
-    """Return displacements and forces from disp_dataset.
-
-    Note
-    ----
-    Dipslacements and forces of all atoms in supercells are returned.
-
-    Parameters
-    ----------
-    disp_dataset : dict
-        Displacement dataset.
-
-    Returns
-    -------
-    displacements : ndarray
-        Displacements of all atoms in all supercells.
-        shape=(snapshots, supercell atoms, 3), dtype='double', order='C'
-    forces : ndarray or None
-        Forces of all atoms in all supercells.
-        shape=(snapshots, supercell atoms, 3), dtype='double', order='C'
-        None is returned when forces don't exist.
-
-    """
-    if "first_atoms" in disp_dataset:
-        natom = disp_dataset["natom"]
-        ndisp = len(disp_dataset["first_atoms"])
-        for disp1 in disp_dataset["first_atoms"]:
-            ndisp += len(disp1["second_atoms"])
-        displacements = np.zeros((ndisp, natom, 3), dtype="double", order="C")
-        indices = []
-        count = 0
-        for disp1 in disp_dataset["first_atoms"]:
-            indices.append(count)
-            displacements[count, disp1["number"]] = disp1["displacement"]
-            count += 1
-
-        for disp1 in disp_dataset["first_atoms"]:
-            for disp2 in disp1["second_atoms"]:
-                if "included" in disp2:
-                    if disp2["included"]:
-                        indices.append(count)
-                else:
-                    indices.append(count)
-                displacements[count, disp1["number"]] = disp1["displacement"]
-                displacements[count, disp2["number"]] = disp2["displacement"]
-                count += 1
-
-        return np.array(displacements[indices], dtype="double", order="C")
 
-    elif "forces" in disp_dataset and "displacements" in disp_dataset:
-        return disp_dataset["displacements"]
+        if forces_count == 0:
+            forces = None
+        else:
+            forces = np.array(forces[indices], dtype="double", order="C")
+            assert forces_count == count
+
+        displacements = np.array(displacements[indices], dtype="double", order="C")
+        return displacements, forces
+    elif "displacements" in disp_dataset:
+        displacements = disp_dataset["displacements"]
+        if "forces" in disp_dataset:
+            forces = disp_dataset["forces"]
+        else:
+            forces = None
+        return displacements, forces
     else:
         raise RuntimeError("disp_dataset doesn't contain correct information.")