diff --git a/doc/deoplete.txt b/doc/deoplete.txt
index f9ecd77b..6cad145d 100644
--- a/doc/deoplete.txt
+++ b/doc/deoplete.txt
@@ -64,7 +64,7 @@ You can enable Python3 interface with pip: >
 
     pip3 install neovim
 
-Note: deoplete needs neovim-python ver.0.1.8+.
+Note: deoplete needs neovim-python ver.0.2.4+.
 You need update neovim-python module.
 >
     pip3 install --upgrade neovim
diff --git a/rplugin/python3/deoplete/deoplete.py b/rplugin/python3/deoplete/deoplete.py
index 6bbbc42a..24e43bb1 100644
--- a/rplugin/python3/deoplete/deoplete.py
+++ b/rplugin/python3/deoplete/deoplete.py
@@ -6,8 +6,7 @@
 
 from deoplete import logger
 from deoplete.parent import Parent
-from deoplete.util import (error_tb, find_rplugins)
-# from deoplete.util import error
+from deoplete.util import (error_tb, find_rplugins, error)
 
 
 class Deoplete(logger.LoggingMixin):
@@ -27,6 +26,10 @@ def __init__(self, vim):
         self._max_parents = max(
             [1, self._vim.vars['deoplete#num_processes']])
 
+        if self._max_parents > 1 and not hasattr(self._vim, 'loop'):
+            error(self._vim, 'neovim-python 0.2.4+ is required.')
+            return
+
         # Enable logging before "Init" for more information, and e.g.
         # deoplete-jedi picks up the log filename from deoplete's handler in
         # its on_init.
@@ -82,7 +85,8 @@ def completion_begin(self, context):
         # Check the previous completion
         prev_candidates = context['vars'][
             'deoplete#_prev_completion']['candidates']
-        if context['event'] == 'Async' and candidates == prev_candidates:
+        if (context['event'] == 'Async' and
+                not prev_candidates and candidates == prev_candidates):
             return
 
         # error(self._vim, candidates)
diff --git a/rplugin/python3/deoplete/parent.py b/rplugin/python3/deoplete/parent.py
index a22b9798..2ba08aea 100644
--- a/rplugin/python3/deoplete/parent.py
+++ b/rplugin/python3/deoplete/parent.py
@@ -5,6 +5,11 @@
 # ============================================================================
 
 import time
+import os
+import msgpack
+import subprocess
+from functools import partial
+from queue import Queue
 
 from deoplete import logger
 from deoplete.process import Process
@@ -17,10 +22,20 @@ def __init__(self, vim, context):
         self.name = 'parent'
 
         self._vim = vim
-        self._proc = None
+        self._hnd = None
+        self._stdin = None
         self._child = None
         self._queue_id = ''
         self._prev_pos = []
+        self._queue_in = Queue()
+        self._queue_out = Queue()
+        self._packer = msgpack.Packer(
+            use_bin_type=True,
+            encoding='utf-8',
+            unicode_errors='surrogateescape')
+        self._unpacker = msgpack.Unpacker(
+            encoding='utf-8',
+            unicode_errors='surrogateescape')
         self._start_process(context)
 
     def enable_logging(self):
@@ -65,48 +80,65 @@ def merge_results(self, context):
 
     def on_event(self, context):
         self._put('on_event', [context])
-        if context['event'] == 'VimLeavePre':
-            self._stop_process()
 
     def _start_process(self, context):
         if self._vim.vars['deoplete#num_processes'] > 1:
             # Parallel
-            python3 = self._vim.vars.get('python3_host_prog', 'python3')
-            self._proc = Process(
-                [python3, context['dp_main'],
-                 self._vim.vars['deoplete#_serveraddr']],
-                context, context['cwd'])
+
+            startupinfo = None
+            if os.name == 'nt':
+                startupinfo = subprocess.STARTUPINFO()
+                startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
+
+            self._hnd = self._vim.loop.create_task(
+                self._vim.loop.subprocess_exec(
+                    partial(Process, self),
+                    self._vim.vars.get('python3_host_prog', 'python3'),
+                    context['dp_main'],
+                    self._vim.vars['deoplete#_serveraddr'],
+                    stderr=None, cwd=context['cwd'], startupinfo=startupinfo))
         else:
             # Serial
             from deoplete.child import Child
             self._child = Child(self._vim)
 
-    def _stop_process(self):
-        if self._proc:
-            self._proc.kill()
-            self._proc = None
-
     def _put(self, name, args):
         queue_id = str(time.time())
 
-        if self._proc:
+        if self._child:
+            return self._child.main(name, args, queue_id)
+
+        if not self._hnd:
+            return None
+
+        msg = self._packer.pack({
+            'name': name, 'args': args, 'queue_id': queue_id
+        })
+        self._queue_in.put(msg)
+
+        if self._stdin:
             try:
-                self._proc.write({
-                    'name': name, 'args': args, 'queue_id': queue_id
-                })
+                while not self._queue_in.empty():
+                    self._stdin.write(self._queue_in.get_nowait())
             except BrokenPipeError as e:
                 error_tb(self._vim, 'Crash in child process')
                 error(self._vim, 'stderr=' + str(self._proc.read_error()))
-                self._proc.kill()
-            return queue_id
-        elif self._child:
-            return self._child.main(name, args, queue_id)
-        else:
-            return None
+                self._hnd = None
+        return queue_id
 
     def _get(self, queue_id):
-        if not self._proc:
+        if not self._hnd:
             return []
 
-        return [x for x in self._proc.communicate(0.02)
-                if x['queue_id'] == queue_id]
+        outs = []
+        while not self._queue_out.empty():
+            outs.append(self._queue_out.get_nowait())
+        return [x for x in outs if x['queue_id'] == queue_id]
+
+    def _on_connection(self, transport):
+        self._stdin = transport.get_pipe_transport(0)
+
+    def _on_output(self, fd, data):
+        self._unpacker.feed(data)
+        for child_out in self._unpacker:
+            self._queue_out.put(child_out)
diff --git a/rplugin/python3/deoplete/process.py b/rplugin/python3/deoplete/process.py
index c85e3d48..54ac3e72 100644
--- a/rplugin/python3/deoplete/process.py
+++ b/rplugin/python3/deoplete/process.py
@@ -4,80 +4,20 @@
 # License: MIT license
 # ============================================================================
 
-import subprocess
-import os
-import msgpack
-from threading import Thread
-from queue import Queue
-from time import time, sleep
+import asyncio
 
 
-class Process(object):
-    def __init__(self, commands, context, cwd):
-        startupinfo = None
-        if os.name == 'nt':
-            startupinfo = subprocess.STARTUPINFO()
-            startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
-        self._proc = subprocess.Popen(commands,
-                                      stdin=subprocess.PIPE,
-                                      stdout=subprocess.PIPE,
-                                      stderr=subprocess.PIPE,
-                                      startupinfo=startupinfo,
-                                      cwd=cwd)
-        self._context = context
-        self._packer = msgpack.Packer(
-            use_bin_type=True,
-            encoding='utf-8',
-            unicode_errors='surrogateescape')
-        self._unpacker = msgpack.Unpacker(
-            encoding='utf-8',
-            unicode_errors='surrogateescape')
-        self._queue_out = Queue()
-        self._thread = Thread(target=self.enqueue_output)
-        self._thread.start()
+class Process(asyncio.SubprocessProtocol):
 
-    def kill(self):
-        if not self._proc:
-            return
-        self._proc.kill()
-        self._proc.wait()
-        self._proc = None
-        self._queue_out = None
-        self._thread.join(1.0)
-        self._thread = None
+    def __init__(self, plugin):
+        self._plugin = plugin
+        self._vim = plugin._vim
 
-    def enqueue_output(self):
-        while self._proc and self._proc.stdout:
-            b = self._proc.stdout.raw.read(102400)
-            if b is None:
-                continue
-            if b == b'':
-                # EOF
-                break
-            self._unpacker.feed(b)
-            for child_out in self._unpacker:
-                self._queue_out.put(child_out)
+    def connection_made(self, transport):
+        self._vim.async_call(self._plugin._on_connection, transport)
 
-    def communicate(self, timeout):
-        if not self._proc:
-            return []
+    def pipe_data_received(self, fd, data):
+        self._vim.async_call(self._plugin._on_output, fd, data)
 
-        end = time() + timeout
-        while self._queue_out.empty() and time() < end:
-            sleep(0.005)
-
-        outs = []
-        while not self._queue_out.empty():
-            outs.append(self._queue_out.get_nowait())
-        return outs
-
-    def read_error(self):
-        if not self._proc or not self._proc.stderr:
-            return ''
-        return self._proc.stderr.read()
-
-    def write(self, expr):
-        if not self._proc or not self._proc.stdin:
-            return
-        self._proc.stdin.write(self._packer.pack(expr))
-        self._proc.stdin.flush()
+    def process_exited(self):
+        pass