diff --git a/app/models/post.rb b/app/models/post.rb
index eff7d4b52..4833485aa 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -705,6 +705,8 @@ class Post < ApplicationRecord
       normalized_tags = TagAlias.to_aliased(normalized_tags)
       normalized_tags = %w(tagme) if normalized_tags.empty?
       normalized_tags = add_automatic_tags(normalized_tags)
+      normalized_tags = remove_invalid_tags(normalized_tags)
+      normalized_tags = Tag.convert_cosplay_tags(normalized_tags)
       normalized_tags = normalized_tags + Tag.create_for_list(TagImplication.automatic_tags_for(normalized_tags))
       normalized_tags = TagImplication.with_descendants(normalized_tags)
       normalized_tags = normalized_tags.compact.uniq.sort
@@ -712,6 +714,14 @@ class Post < ApplicationRecord
       set_tag_string(normalized_tags.join(" "))
     end
 
+    def remove_invalid_tags(tags)
+      invalid_tags = Tag.invalid_cosplay_tags(tags)
+      if invalid_tags.present?
+        self.warnings[:base] << "The root tag must be a character tag: #{invalid_tags.map {|tag| "[b]#{tag}[/b]" }.join(", ")}"
+      end
+      tags - invalid_tags
+    end
+
     def remove_negated_tags(tags)
       @negated_tags, tags = tags.partition {|x| x =~ /\A-/i}
       @negated_tags = @negated_tags.map {|x| x[1..-1]}
diff --git a/app/models/tag.rb b/app/models/tag.rb
index 8070350cd..ea9b2f32e 100644
--- a/app/models/tag.rb
+++ b/app/models/tag.rb
@@ -950,6 +950,19 @@ class Tag < ApplicationRecord
     end
   end
 
+  def self.convert_cosplay_tags(tags)
+    cosplay_tags,other_tags = tags.partition {|tag| tag.match(/\A(.+)_\(cosplay\)\Z/) }
+    cosplay_tags.grep(/\A(.+)_\(cosplay\)\Z/) { "#{TagAlias.to_aliased([$1]).first}_(cosplay)" } + other_tags
+  end
+
+  def self.invalid_cosplay_tags(tags)
+    tags.grep(/\A(.+)_\(cosplay\)\Z/) {|match| [match,TagAlias.to_aliased([$1]).first] }.
+      select do |name|
+        tag = Tag.find_by_name(name[1])
+        !tag.nil? && tag.category != Tag.categories.character
+      end.map {|tag| tag[0]}
+  end
+
   def editable_by?(user)
     return true if user.is_admin?
     return true if !is_locked? && user.is_builder? && post_count < 1_000