diff --git a/src-ui/res/history.en.yaml b/src-ui/res/history.en.yaml
index c221bf54d..037754afe 100644
--- a/src-ui/res/history.en.yaml
+++ b/src-ui/res/history.en.yaml
@@ -241,3 +241,4 @@ nuriloop: This genre first appeared in Puzzle Communication Nikoli vol. 62.
 ruleofthree: This genre was invented by Seren.
 compass: This genre was invented by Silke Berendes.
 soulmates: This genre was invented by GESAKU.
+longest: This genre was invented by GESAKU.
diff --git a/src-ui/res/history.ja.yaml b/src-ui/res/history.ja.yaml
index ccbae520d..172b41c04 100644
--- a/src-ui/res/history.ja.yaml
+++ b/src-ui/res/history.ja.yaml
@@ -239,3 +239,4 @@ kissing: ''
 topo: ''
 nuriloop: パズル通信ニコリ vol.62より
 soulmates: GESAKU氏考案
+longest: GESAKU氏考案
diff --git a/src-ui/res/rules.en.yaml b/src-ui/res/rules.en.yaml
index e29caa0a2..9b4a4b854 100644
--- a/src-ui/res/rules.en.yaml
+++ b/src-ui/res/rules.en.yaml
@@ -486,3 +486,7 @@ golemgrad: |-
   4. A number indicates the size of the region that contains it.
   5. All cells used by lines must form an orthogonally contiguous area.
   6. The cells used by lines cannot form a 2x2 square.
+longest: |-
+  Draw lines over the dotted lines to divide the board into polygons.
+  1. For each polygon, the side (or sides) with the biggest length must consist entirely of given borders.
+  2. Each given border must be part of the longest side for at least one of the adjacent polygons.
diff --git a/src-ui/res/rules.ja.yaml b/src-ui/res/rules.ja.yaml
index 90c3bc458..17bbaf19e 100644
--- a/src-ui/res/rules.ja.yaml
+++ b/src-ui/res/rules.ja.yaml
@@ -405,3 +405,6 @@ golemgrad: |-
   7. すべての黒マスは、タテヨコに全体でひとつながりになっていなければなりません。
   8. 数字の入ったマスを黒マスにしてはいけません。
   9. 黒マスが2×2のカタマリになってはいけません。
+longest: |-
+  1. 点線上に線を引き、面積1マス以上のブロックに分割します。使わないマスはありません。
+  2. 最初から表示されている線は各ブロックの最も長い辺(複数あるならすべて)です。書き込む線が最も長い辺の一部や全体になるようなブロックができてはいけません。
diff --git a/src/res/failcode.en.json b/src/res/failcode.en.json
index de5d32fae..9fc35159f 100644
--- a/src/res/failcode.en.json
+++ b/src/res/failcode.en.json
@@ -24,7 +24,7 @@
     "arAlone.toichika2": "A number can not see an identical number.",
     "arBlkEdge.loute": "An arrow is not at the endpoint of an area.",
     "arBlocked.toichika2": "Other numbers are between a pair of numbers.",
-    "arBlockLt2.evolmino": "The arrow passes through less than two blocks.",
+    "arBlockLt2.evolmino": "The arrow passes through fewer than two blocks.",
     "arCountGt.arrowflow": "A number has too many arrows pointing towards it.",
     "arCountLt.arrowflow": "A number does not have enough arrows pointing towards it.",
     "arDistance.distopia": "A number is not equal to the sum of the closest distances.",
@@ -686,7 +686,7 @@
     "lnOnShade.recoil": "There is a line on a recoiled cell.",
     "lnOnShade.yajisoko": "A line goes over a shaded cell.",
     "lnOnShade": "There is a line on a shaded cell.",
-    "lnOnWhite.uturns":"A white circle is not in the middle of a line.",
+    "lnOnWhite.uturns": "A white circle is not in the middle of a line.",
     "lnOverlap.kouchoku": "Some segments overlap.",
     "lnOverlap.tontti": "A line overlaps a number.",
     "lnPassOver.kouchoku": "A segment passes over a clue.",