diff --git a/backend/app/controllers/tags_controller.rb b/backend/app/controllers/tags_controller.rb
index 7c6feac..26c2fee 100644
--- a/backend/app/controllers/tags_controller.rb
+++ b/backend/app/controllers/tags_controller.rb
@@ -218,63 +218,16 @@ class TagsController < ApplicationController
     locale = resolve_locale!
 
     q = params[:q].to_s.strip.sub(/\Anot:/i, '')
-    prefix = "#{ ActiveRecord::Base.sanitize_sql_like(q) }%"
+    literal = ActiveRecord::Base.sanitize_sql_like(q)
+    nico = bool?(:nico, default: true)
+    present = bool?(:present, default: true)
 
-    with_nico = bool?(:nico, default: true)
-    present_only = bool?(:present, default: true)
-
-    alias_rows =
-        TagName
-        .where(language_code: locale.language_code, primary_flg: false)
-        .where('name LIKE ?', prefix)
-        .pluck(:tag_id, :name)
-
-    matched_alias_by_tag_id = { }
-    tag_ids = []
-    alias_rows.each do |tag_id, alias_name|
-      tag_ids << tag_id
-      matched_alias_by_tag_id[tag_id] ||= alias_name
+    rows = autocomplete_rows(locale:, pattern: "#{ literal }%", nico:, present:)
+    if rows.length < 20 && q.present?
+      suffix_rows = autocomplete_rows(locale:, pattern: "%#{ literal }", nico:, present:)
+      rows = (rows + suffix_rows).uniq { [_1['category'], _1['id']] }.first(20)
     end
 
-    base =
-        Tag
-        .joins(:tag_names)
-        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
-                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
-        .where(tag_names: { language_code: locale.language_code, primary_flg: true },
-               deprecated_at: nil)
-    base = base.where('tags.post_count > 0') if present_only
-
-    canonical_hit = base.where('tag_names.name LIKE ?', prefix)
-
-    internal_tags = canonical_hit.or(base.where(id: tag_ids.uniq))
-
-    internal_rows =
-        internal_tags
-        .order(Arel.sql('tags.post_count DESC, tag_names.name'))
-        .limit(20)
-        .map { |tag|
-          TagRepr.base(tag, language_code: locale.language_code)
-                 .merge(matched_alias: matched_alias_by_tag_id[tag.id])
-        }
-
-    return render json: internal_rows unless with_nico
-
-    external_base = ExternalTag.all
-    external_base = external_base.where('post_count > 0') if present_only
-
-    external_rows =
-        external_base
-        .where("CONCAT(platform, ':', name) LIKE ? OR name LIKE ?", prefix, prefix)
-        .order(post_count: :desc, name: :asc)
-        .limit(20)
-        .map { external_tag_json(_1) }
-
-    rows =
-    (internal_rows + external_rows)
-        .sort_by { |row| [-row['post_count'], row['name'] || row[:name]] }
-        .first(20)
-
     render json: rows
   end
 
@@ -545,6 +498,59 @@ class TagsController < ApplicationController
 
   private
 
+  def autocomplete_rows locale:, pattern:, nico:, present:
+    alias_rows =
+        TagName
+        .where(language_code: locale.language_code, primary_flg: false)
+        .where('name LIKE ?', pattern)
+        .pluck(:tag_id, :name)
+
+    matched_alias_by_tag_id = { }
+    tag_ids = []
+    alias_rows.each do |tag_id, alias_name|
+      tag_ids << tag_id
+      matched_alias_by_tag_id[tag_id] ||= alias_name
+    end
+
+    base =
+        Tag
+        .joins(:tag_names)
+        .preload(:tag_names, :materials, :deerjikists, :tag_descriptions,
+                 parents: [:tag_names, :materials, :deerjikists, :tag_descriptions])
+        .where(tag_names: { language_code: locale.language_code, primary_flg: true },
+               deprecated_at: nil)
+    base = base.where('tags.post_count > 0') if present
+
+    canonical_hit = base.where('tag_names.name LIKE ?', pattern)
+
+    internal_tags = canonical_hit.or(base.where(id: tag_ids.uniq))
+
+    internal_rows =
+        internal_tags
+        .order(Arel.sql('tags.post_count DESC, tag_names.name'))
+        .limit(20)
+        .map { |tag|
+          TagRepr.base(tag, language_code: locale.language_code)
+                 .merge(matched_alias: matched_alias_by_tag_id[tag.id])
+        }
+
+    return internal_rows unless nico
+
+    external_base = ExternalTag.all
+    external_base = external_base.where('post_count > 0') if present
+
+    external_rows =
+        external_base
+        .where("CONCAT(platform, ':', name) LIKE ? OR name LIKE ?", pattern, pattern)
+        .order(post_count: :desc, name: :asc)
+        .limit(20)
+        .map { external_tag_json(_1) }
+
+    (internal_rows + external_rows)
+        .sort_by { |row| [-row['post_count'], row['name'] || row[:name]] }
+        .first(20)
+  end
+
   def material_filter_param default:
     value = params[:material_filter].to_s.presence
     return default unless ['present', 'missing', 'any'].include?(value)