diff --git a/benches/japanese-language-transformer.bench.js b/benches/japanese-language-transformer.bench.js
index ce0910cbd1..4206805cf0 100644
--- a/benches/japanese-language-transformer.bench.js
+++ b/benches/japanese-language-transformer.bench.js
@@ -78,7 +78,9 @@ describe('japanese language transformer', () => {
             '食べぬ',
             '食べ',
             '食べましょう',
+            '食べましょっか',
             '食べよう',
+            '食べよっか',
             '食べるまい',
             '食べまい',
             '食べとく',
@@ -145,7 +147,9 @@ describe('japanese language transformer', () => {
             'こねば',
             'き',
             'きましょう',
+            'きましょっか',
             'こよう',
+            'こよっか',
             'くるまい',
             'こまい',
             'きとく',
@@ -209,7 +213,9 @@ describe('japanese language transformer', () => {
             'せざる',
             'せねば',
             'しましょう',
+            'しましょっか',
             'しよう',
+            'しよっか',
             'するまい',
             'しまい',
             'しとく',
diff --git a/ext/js/language/ja/japanese-transforms.js b/ext/js/language/ja/japanese-transforms.js
index 7479fd3b18..7e4338c479 100644
--- a/ext/js/language/ja/japanese-transforms.js
+++ b/ext/js/language/ja/japanese-transforms.js
@@ -1287,7 +1287,7 @@ export const japaneseTransforms = {
         },
         'volitional': {
             name: 'volitional',
-            description: '1. Expresses speaker\'s will or intention; volitional form.\n' +
+            description: '1. Expresses speaker\'s will or intention.\n' +
             '2. Expresses an invitation to the other party.\n' +
             '3. (Used in …ようとする) Indicates being on the verge of initiating an action or transforming a state.\n' +
             '4. Indicates an inference of a matter.\n' +
@@ -1322,6 +1322,33 @@ export const japaneseTransforms = {
                 suffixInflection('かろう', 'い', [], ['adj-i']),
             ],
         },
+        'volitional slang': {
+            name: 'volitional slang',
+            description: 'Contraction of volitional form + か\n' +
+            '1. Expresses speaker\'s will or intention.\n' +
+            '2. Expresses an invitation to the other party.\n' +
+            'Usage: Replace final う with っ of volitional form then add か.\n' +
+            'For example: 行こうか -> 行こっか.',
+            rules: [
+                suffixInflection('よっか', 'る', [], ['v1']),
+                suffixInflection('おっか', 'う', [], ['v5']),
+                suffixInflection('こっか', 'く', [], ['v5']),
+                suffixInflection('ごっか', 'ぐ', [], ['v5']),
+                suffixInflection('そっか', 'す', [], ['v5']),
+                suffixInflection('とっか', 'つ', [], ['v5']),
+                suffixInflection('のっか', 'ぬ', [], ['v5']),
+                suffixInflection('ぼっか', 'ぶ', [], ['v5']),
+                suffixInflection('もっか', 'む', [], ['v5']),
+                suffixInflection('ろっか', 'る', [], ['v5']),
+                suffixInflection('じよっか', 'ずる', [], ['vz']),
+                suffixInflection('しよっか', 'する', [], ['vs']),
+                suffixInflection('為よっか', '為る', [], ['vs']),
+                suffixInflection('こよっか', 'くる', [], ['vk']),
+                suffixInflection('来よっか', '来る', [], ['vk']),
+                suffixInflection('來よっか', '來る', [], ['vk']),
+                suffixInflection('ましょっか', 'ます', [], ['-masu']),
+            ],
+        },
         '-mai': {
             name: '-mai',
             description: 'Negative volitional form of verbs.\n' +
diff --git a/test/language/japanese-transforms.test.js b/test/language/japanese-transforms.test.js
index a506c4c1e4..428e0f4b9b 100644
--- a/test/language/japanese-transforms.test.js
+++ b/test/language/japanese-transforms.test.js
@@ -99,7 +99,9 @@ const tests = [
             {term: '食べる', source: '食べにゃ',         rule: 'v1', reasons: ['-neba', '-ya']},
             {term: '食べる', source: '食べ',             rule: 'v1d', reasons: ['continuative']},
             {term: '食べる', source: '食べましょう',     rule: 'v1', reasons: ['-masu', 'volitional']},
+            {term: '食べる', source: '食べましょっか',         rule: 'v1', reasons: ['-masu', 'volitional slang']},
             {term: '食べる', source: '食べよう',         rule: 'v1', reasons: ['volitional']},
+            {term: '食べる', source: '食べよっか',       rule: 'v1', reasons: ['volitional slang']},
             {term: '食べる', source: '食べるまい',      rule: 'v1', reasons: ['-mai']},
             {term: '食べる', source: '食べまい',      rule: 'v1', reasons: ['-mai']},
             // ['causative-passive']
@@ -164,7 +166,9 @@ const tests = [
             {term: '買う', source: '買わにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '買う', source: '買い',             rule: 'v5', reasons: ['continuative']},
             {term: '買う', source: '買いましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '買う', source: '買いましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '買う', source: '買おう',           rule: 'v5', reasons: ['volitional']},
+            {term: '買う', source: '買おっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '買う', source: '買うまい',       rule: 'v5', reasons: ['-mai']},
             {term: '買う', source: '買わされる',       rule: 'v5', reasons: ['causative-passive']},
             {term: '買う', source: '買っとく',         rule: 'v5', reasons: ['-toku']},
@@ -233,7 +237,9 @@ const tests = [
             {term: '行く', source: '行かにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '行く', source: '行き',             rule: 'v5', reasons: ['continuative']},
             {term: '行く', source: '行きましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '行く', source: '行きましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '行く', source: '行こう',           rule: 'v5', reasons: ['volitional']},
+            {term: '行く', source: '行こっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '行く', source: '行くまい',       rule: 'v5', reasons: ['-mai']},
             {term: '行く', source: '行かされる',       rule: 'v5', reasons: ['causative-passive']},
             {term: '行く', source: '行いとく',         rule: 'v5', reasons: ['-toku']},
@@ -302,7 +308,9 @@ const tests = [
             {term: '泳ぐ', source: '泳がにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '泳ぐ', source: '泳ぎ',             rule: 'v5', reasons: ['continuative']},
             {term: '泳ぐ', source: '泳ぎましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '泳ぐ', source: '泳ぎましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '泳ぐ', source: '泳ごう',           rule: 'v5', reasons: ['volitional']},
+            {term: '泳ぐ', source: '泳ごっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '泳ぐ', source: '泳ぐまい',       rule: 'v5', reasons: ['-mai']},
             {term: '泳ぐ', source: '泳がされる',       rule: 'v5', reasons: ['causative-passive']},
             {term: '泳ぐ', source: '泳いどく',         rule: 'v5', reasons: ['-toku']},
@@ -370,7 +378,9 @@ const tests = [
             {term: '話す', source: '話さにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '話す', source: '話し',             rule: 'v5', reasons: ['continuative']},
             {term: '話す', source: '話しましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '話す', source: '話しましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '話す', source: '話そう',           rule: 'v5', reasons: ['volitional']},
+            {term: '話す', source: '話そっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '話す', source: '話すまい',       rule: 'v5', reasons: ['-mai']},
             // ['causative-passive']
             {term: '話す', source: '話しとく',         rule: 'v5', reasons: ['-toku']},
@@ -444,7 +454,9 @@ const tests = [
             {term: '待つ', source: '待たにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '待つ', source: '待ち',             rule: 'v5', reasons: ['continuative']},
             {term: '待つ', source: '待ちましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '待つ', source: '待ちましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '待つ', source: '待とう',           rule: 'v5', reasons: ['volitional']},
+            {term: '待つ', source: '待とっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '待つ', source: '待つまい',       rule: 'v5', reasons: ['-mai']},
             {term: '待つ', source: '待たされる',       rule: 'v5', reasons: ['causative-passive']},
             {term: '待つ', source: '待っとく',         rule: 'v5', reasons: ['-toku']},
@@ -513,7 +525,9 @@ const tests = [
             {term: '死ぬ', source: '死なにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '死ぬ', source: '死に',             rule: 'v5', reasons: ['continuative']},
             {term: '死ぬ', source: '死にましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '死ぬ', source: '死にましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '死ぬ', source: '死のう',           rule: 'v5', reasons: ['volitional']},
+            {term: '死ぬ', source: '死のっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '死ぬ', source: '死ぬまい',       rule: 'v5', reasons: ['-mai']},
             {term: '死ぬ', source: '死なされる',       rule: 'v5', reasons: ['causative-passive']},
             {term: '死ぬ', source: '死んどく',         rule: 'v5', reasons: ['-toku']},
@@ -581,7 +595,9 @@ const tests = [
             {term: '遊ぶ', source: '遊ばにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '遊ぶ', source: '遊び',             rule: 'v5', reasons: ['continuative']},
             {term: '遊ぶ', source: '遊びましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '遊ぶ', source: '遊びましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '遊ぶ', source: '遊ぼう',           rule: 'v5', reasons: ['volitional']},
+            {term: '遊ぶ', source: '遊ぼっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '遊ぶ', source: '遊ぶまい',       rule: 'v5', reasons: ['-mai']},
             {term: '遊ぶ', source: '遊ばされる',       rule: 'v5', reasons: ['causative-passive']},
             {term: '遊ぶ', source: '遊んどく',         rule: 'v5', reasons: ['-toku']},
@@ -649,7 +665,9 @@ const tests = [
             {term: '飲む', source: '飲まにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '飲む', source: '飲み',             rule: 'v5', reasons: ['continuative']},
             {term: '飲む', source: '飲みましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '飲む', source: '飲みましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '飲む', source: '飲もう',           rule: 'v5', reasons: ['volitional']},
+            {term: '飲む', source: '飲もっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '飲む', source: '飲むまい',       rule: 'v5', reasons: ['-mai']},
             {term: '飲む', source: '飲まされる',       rule: 'v5', reasons: ['causative-passive']},
             {term: '飲む', source: '飲んどく',         rule: 'v5', reasons: ['-toku']},
@@ -715,7 +733,9 @@ const tests = [
             {term: '作る', source: '作らにゃ',         rule: 'v5', reasons: ['-neba', '-ya']},
             {term: '作る', source: '作り',             rule: 'v5', reasons: ['continuative']},
             {term: '作る', source: '作りましょう',     rule: 'v5', reasons: ['-masu', 'volitional']},
+            {term: '作る', source: '作りましょっか',     rule: 'v5', reasons: ['-masu', 'volitional slang']},
             {term: '作る', source: '作ろう',           rule: 'v5', reasons: ['volitional']},
+            {term: '作る', source: '作ろっか',           rule: 'v5', reasons: ['volitional slang']},
             {term: '作る', source: '作るまい',       rule: 'v5', reasons: ['-mai']},
             {term: '作る', source: '作らされる',       rule: 'v5', reasons: ['causative-passive']},
             {term: '作る', source: '作っとく',         rule: 'v5', reasons: ['-toku']},
@@ -788,7 +808,9 @@ const tests = [
             {term: '為る', source: '為にゃ',         rule: 'vs', reasons: ['-neba', '-ya']},
             // ['continuative']
             {term: '為る', source: '為ましょう',     rule: 'vs', reasons: ['-masu', 'volitional']},
+            {term: '為る', source: '為ましょっか',     rule: 'vs', reasons: ['-masu', 'volitional slang']},
             {term: '為る', source: '為よう',         rule: 'vs', reasons: ['volitional']},
+            {term: '為る', source: '為よっか',         rule: 'vs', reasons: ['volitional slang']},
             {term: '為る', source: '為るまい',       rule: 'vs', reasons: ['-mai']},
             {term: '為る', source: '為まい',       rule: 'vs', reasons: ['-mai']},
             // ['causative-passive']
@@ -859,7 +881,9 @@ const tests = [
             {term: 'する', source: 'せにゃ',         rule: 'vs', reasons: ['-neba', '-ya']},
             {term: 'する', source: 'し',             rule: 'vs', reasons: ['continuative']},
             {term: 'する', source: 'しましょう',     rule: 'vs', reasons: ['-masu', 'volitional']},
+            {term: 'する', source: 'しましょっか',     rule: 'vs', reasons: ['-masu', 'volitional slang']},
             {term: 'する', source: 'しよう',         rule: 'vs', reasons: ['volitional']},
+            {term: 'する', source: 'しよっか',         rule: 'vs', reasons: ['volitional slang']},
             {term: 'する', source: 'するまい',       rule: 'vs', reasons: ['-mai']},
             {term: 'する', source: 'しまい',       rule: 'vs', reasons: ['-mai']},
             {term: 'する', source: 'しなきゃ',        rule: 'vs', reasons: ['negative', '-ba', '-ya']},
@@ -925,7 +949,9 @@ const tests = [
             {term: '来る', source: '来にゃ',         rule: 'vk', reasons: ['-neba', '-ya']},
             {term: '来る', source: '来',             rule: 'vk', reasons: ['continuative']},
             {term: '来る', source: '来ましょう',     rule: 'vk', reasons: ['-masu', 'volitional']},
+            {term: '来る', source: '来ましょっか',     rule: 'vk', reasons: ['-masu', 'volitional slang']},
             {term: '来る', source: '来よう',         rule: 'vk', reasons: ['volitional']},
+            {term: '来る', source: '来よっか',         rule: 'vk', reasons: ['volitional slang']},
             {term: '来る', source: '来るまい',       rule: 'vk', reasons: ['-mai']},
             {term: '来る', source: '来まい',       rule: 'vk', reasons: ['-mai']},
             // ['causative-passive']
@@ -990,7 +1016,9 @@ const tests = [
             {term: '來る', source: '來にゃ',         rule: 'vk', reasons: ['-neba', '-ya']},
             {term: '來る', source: '來',             rule: 'vk', reasons: ['continuative']},
             {term: '來る', source: '來ましょう',     rule: 'vk', reasons: ['-masu', 'volitional']},
+            {term: '來る', source: '來ましょっか',     rule: 'vk', reasons: ['-masu', 'volitional slang']},
             {term: '來る', source: '來よう',         rule: 'vk', reasons: ['volitional']},
+            {term: '來る', source: '來よっか',         rule: 'vk', reasons: ['volitional slang']},
             {term: '來る', source: '來るまい',       rule: 'vk', reasons: ['-mai']},
             {term: '來る', source: '來まい',       rule: 'vk', reasons: ['-mai']},
             // ['causative-passive']
@@ -1055,7 +1083,9 @@ const tests = [
             {term: 'くる', source: 'こにゃ',         rule: 'vk', reasons: ['-neba', '-ya']},
             {term: 'くる', source: 'き',             rule: 'vk', reasons: ['continuative']},
             {term: 'くる', source: 'きましょう',     rule: 'vk', reasons: ['-masu', 'volitional']},
+            {term: 'くる', source: 'きましょっか',     rule: 'vk', reasons: ['-masu', 'volitional slang']},
             {term: 'くる', source: 'こよう',         rule: 'vk', reasons: ['volitional']},
+            {term: 'くる', source: 'こよっか',         rule: 'vk', reasons: ['volitional slang']},
             {term: 'くる', source: 'くるまい',       rule: 'vk', reasons: ['-mai']},
             {term: 'くる', source: 'こまい',       rule: 'vk', reasons: ['-mai']},
             // ['causative-passive']