Unfortunately the values do not show up automatically in the $user object. So you can use the following to query on a particular field in the additional profile plugin:

if ($user->id > 0) {
  $query = "select profile_value from #__user_profiles where profile_key = 'profile.city' and user_id = " . (int)$user->id;
  $db->setQuery($query);
  $result = $db->loadResult();
  if ($result == "Tokyo") return XXX;
}

Hi,

the #_ gets replaced with the database prefix automatically.

I'd suggest that you take a look at the (prefix)_user_profiles table in your database and double check what the profile_key and profile_value values are that you're relying on. "profile.city" is one of the keys in the Joomla-supplied user plugin, but yours may be different.

Cheers,
Stephen