diff --git a/app/javascript/styles/karasuba.scss b/app/javascript/styles/karasuba.scss
new file mode 100644
index 0000000000..91f922393e
--- /dev/null
+++ b/app/javascript/styles/karasuba.scss
@@ -0,0 +1,2 @@
+@import 'karasuba/variables';
+@import 'application';
\ No newline at end of file
diff --git a/app/javascript/styles/karasuba/variables.scss b/app/javascript/styles/karasuba/variables.scss
new file mode 100644
index 0000000000..db3293a4e6
--- /dev/null
+++ b/app/javascript/styles/karasuba/variables.scss
@@ -0,0 +1,116 @@
+// 758postal Karasuba theme
+// v1.00
+
+$black: #000000; // Kuro
+$white: #ffffff; // Shiro
+$red-600: #bd5cff !default; // Murasaki
+$red-500: #c485ef !default; // Tsutsuji
+$blurple-600: #d51a2a; // Postal-red
+$blurple-500: #dd4855;
+$blurple-400: #e46a74;
+$blurple-300: #ea8d95;
+$grey-600: #575f57;
+$grey-100: #e4e6e4;
+
+$success-green: #8db568 !default; // Matcha
+$error-red: $red-500 !default;
+$warning-red: #8c72ff !default; //Rindou
+$gold-star: #de8937 !default; //Kogane
+
+$red-bookmark: $warning-red;
+
+// Values from the classic Mastodon UI
+$classic-base-color: #001100; // Karasuba
+$classic-primary-color: #a8c6a8;
+$classic-secondary-color: #e9f2e9;
+$classic-highlight-color: $blurple-500;
+
+// Variables for defaults in UI
+$base-shadow-color: $black !default;
+$base-overlay-background: $black !default;
+$base-border-color: $white !default;
+$simple-background-color: $white !default;
+$valid-value-color: $success-green !default;
+$error-value-color: $error-red !default;
+
+// Tell UI to use selected colors
+$ui-base-color: $classic-base-color !default; // Darkest
+$ui-base-lighter-color: lighten(
+  $ui-base-color,
+  26%
+) !default; // Lighter darkest
+$ui-primary-color: $classic-primary-color !default; // Lighter
+$ui-secondary-color: $classic-secondary-color !default; // Lightest
+$ui-highlight-color: $classic-highlight-color !default;
+$ui-button-color: $white !default;
+$ui-button-background-color: $blurple-500 !default;
+$ui-button-focus-background-color: $blurple-600 !default;
+$ui-button-focus-outline-color: $blurple-400 !default;
+$ui-button-focus-outline: solid 2px $ui-button-focus-outline-color !default;
+
+$ui-button-secondary-color: $blurple-500 !default;
+$ui-button-secondary-border-color: $blurple-500 !default;
+$ui-button-secondary-focus-border-color: $blurple-300 !default;
+$ui-button-secondary-focus-color: $blurple-300 !default;
+
+$ui-button-tertiary-color: $blurple-300 !default;
+$ui-button-tertiary-border-color: $blurple-300 !default;
+$ui-button-tertiary-focus-background-color: $blurple-600 !default;
+$ui-button-tertiary-focus-color: $white !default;
+
+$ui-button-destructive-background-color: $red-500 !default;
+$ui-button-destructive-focus-background-color: $red-600 !default;
+
+$ui-button-icon-focus-outline: $ui-button-focus-outline !default;
+$ui-button-icon-hover-background-color: rgba(255, 101, 120, 40%) !default;
+
+// Variables for texts
+$primary-text-color: $white !default;
+$darker-text-color: $ui-primary-color !default;
+$dark-text-color: $ui-base-lighter-color !default;
+$secondary-text-color: $ui-secondary-color !default;
+$highlight-text-color: lighten($ui-highlight-color, 8%) !default;
+$action-button-color: $ui-base-lighter-color !default;
+$action-button-focus-color: lighten($ui-base-lighter-color, 4%) !default;
+$passive-text-color: $gold-star !default;
+$active-passive-text-color: $success-green !default;
+
+// For texts on inverted backgrounds
+$inverted-text-color: $ui-base-color !default;
+$lighter-text-color: $ui-base-lighter-color !default;
+$light-text-color: $ui-primary-color !default;
+
+// Language codes that uses CJK fonts
+$cjk-langs: ja, ko, zh-CN, zh-HK, zh-TW;
+
+// Variables for components
+$media-modal-media-max-width: 100%;
+
+// put margins on top and bottom of image to avoid the screen covered by image.
+$media-modal-media-max-height: 80%;
+
+$no-gap-breakpoint: 1175px;
+$mobile-breakpoint: 630px;
+
+$font-sans-serif: 'mastodon-font-sans-serif' !default;
+$font-display: 'mastodon-font-display' !default;
+$font-monospace: 'mastodon-font-monospace' !default;
+
+:root {
+  --dropdown-border-color: #{lighten($ui-base-color, 4%)};
+  --dropdown-background-color: #{rgba(darken($ui-base-color, 8%), 0.9)};
+  --dropdown-shadow: 0 20px 25px -5px #{rgba($base-shadow-color, 0.25)},
+    0 8px 10px -6px #{rgba($base-shadow-color, 0.25)};
+  --modal-background-color: #{rgba(darken($ui-base-color, 8%), 0.7)};
+  --modal-background-variant-color: #{rgba($ui-base-color, 0.7)};
+  --modal-border-color: #{lighten($ui-base-color, 4%)};
+  --background-border-color: #{lighten($ui-base-color, 4%)};
+  --background-filter: blur(10px) saturate(180%) contrast(75%) brightness(70%);
+  --background-color: #{darken($ui-base-color, 8%)};
+  --background-color-tint: #{rgba(darken($ui-base-color, 8%), 0.9)};
+  --surface-background-color: #{darken($ui-base-color, 4%)};
+  --surface-variant-background-color: #{$ui-base-color};
+  --surface-variant-active-background-color: #{lighten($ui-base-color, 4%)};
+  --on-surface-color: #{transparentize($ui-base-color, 0.5)};
+  --avatar-border-radius: 8px;
+}
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 814b9c6e90..e5dc63793f 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -1741,6 +1741,7 @@ en:
     mastodon-light: Mastodon (Light)
     758postal: 758postal Renga (Dark)
     hatoba: 758postal Hatoba (Dark)
+    karasuba: 758postal Karasuba (Dark)
   time:
     formats:
       default: "%b %d, %Y, %H:%M"
diff --git a/config/locales/ja.yml b/config/locales/ja.yml
index 2e7dbb9a1e..894cc7468f 100644
--- a/config/locales/ja.yml
+++ b/config/locales/ja.yml
@@ -1703,6 +1703,7 @@ ja:
     mastodon-light: Mastodon (ライト)
     758postal: 七五八逓信局・煉瓦 (ダーク)
     hatoba: 七五八逓信局・鳩羽 (ダーク)
+    karasuba: 七五八逓信局・烏羽 (ダーク)
   time:
     formats:
       default: "%Y年%m月%d日 %H:%M"
diff --git a/config/themes.yml b/config/themes.yml
index d29fbd8e88..39e0859fb7 100644
--- a/config/themes.yml
+++ b/config/themes.yml
@@ -3,3 +3,4 @@ contrast: styles/contrast.scss
 mastodon-light: styles/mastodon-light.scss
 758postal: styles/758postal.scss
 hatoba: styles/hatoba.scss
+karasuba: styles/karasuba.scss