diff --git a/src/en/kouhaiwork/AndroidManifest.xml b/src/en/kouhaiwork/AndroidManifest.xml
new file mode 100644
index 000000000..30deb7f79
--- /dev/null
+++ b/src/en/kouhaiwork/AndroidManifest.xml
@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest package="eu.kanade.tachiyomi.extension" />
diff --git a/src/en/kouhaiwork/build.gradle b/src/en/kouhaiwork/build.gradle
new file mode 100644
index 000000000..7092fad4b
--- /dev/null
+++ b/src/en/kouhaiwork/build.gradle
@@ -0,0 +1,12 @@
+apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
+apply plugin: 'kotlinx-serialization'
+
+ext {
+    extName = 'Kouhai Scanlations'
+    pkgNameSuffix = 'en.kouhaiwork'
+    extClass = '.KouhaiWork'
+    extVersionCode = 1
+}
+
+apply from: "$rootDir/common.gradle"
diff --git a/src/en/kouhaiwork/res/mipmap-hdpi/ic_launcher.png b/src/en/kouhaiwork/res/mipmap-hdpi/ic_launcher.png
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diff --git a/src/en/kouhaiwork/res/mipmap-xhdpi/ic_launcher.png b/src/en/kouhaiwork/res/mipmap-xhdpi/ic_launcher.png
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diff --git a/src/en/kouhaiwork/res/mipmap-xxhdpi/ic_launcher.png b/src/en/kouhaiwork/res/mipmap-xxhdpi/ic_launcher.png
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diff --git a/src/en/kouhaiwork/res/mipmap-xxxhdpi/ic_launcher.png b/src/en/kouhaiwork/res/mipmap-xxxhdpi/ic_launcher.png
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diff --git a/src/en/kouhaiwork/res/web_hi_res_512.png b/src/en/kouhaiwork/res/web_hi_res_512.png
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diff --git a/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiFilters.kt b/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiFilters.kt
new file mode 100644
index 000000000..01f52eeeb
--- /dev/null
+++ b/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiFilters.kt
@@ -0,0 +1,56 @@
+package eu.kanade.tachiyomi.extension.en.kouhaiwork
+
+import eu.kanade.tachiyomi.source.model.Filter
+
+class Genre(val id: Int, name: String) : Filter.CheckBox(name)
+
+private val genres: List<Genre>
+    get() = listOf(
+        Genre(1, "Romance"),
+        Genre(2, "Comedy"),
+        Genre(3, "Slice of Life"),
+        Genre(4, "Fantasy"),
+        Genre(5, "Sci-Fi"),
+        Genre(6, "Psychological"),
+        Genre(7, "Horror"),
+        Genre(8, "Mystery"),
+        Genre(9, "Girls' Love"),
+        Genre(10, "Drama"),
+        Genre(11, "Action"),
+        Genre(12, "Ecchi"),
+        Genre(13, "Adventure"),
+    )
+
+class GenresFilter(values: List<Genre> = genres) :
+    Filter.Group<Genre>("Genres", values)
+
+class Theme(val id: Int, name: String) : Filter.CheckBox(name)
+
+private val themes: List<Theme>
+    get() = listOf(
+        Theme(1, "Office Workers"),
+        Theme(2, "Family"),
+        Theme(3, "Supernatural"),
+        Theme(4, "Demons"),
+        Theme(5, "Magic"),
+        Theme(6, "Aliens"),
+        Theme(7, "Suggestive"),
+        Theme(8, "Doujinshi"),
+        Theme(9, "School Life"),
+        Theme(10, "Police"),
+    )
+
+class ThemesFilter(values: List<Theme> = themes) :
+    Filter.Group<Theme>("Themes", values)
+
+private val demographics: Array<String>
+    get() = arrayOf("Any", "Shounen", "Shoujo", "Seinen")
+
+class DemographicsFilter(values: Array<String> = demographics) :
+    Filter.Select<String>("Demographic", values)
+
+private val statuses: Array<String>
+    get() = arrayOf("Any", "Ongoing", "Finished", "Axed/Dropped")
+
+class StatusFilter(values: Array<String> = statuses) :
+    Filter.Select<String>("Status", values)
diff --git a/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiModels.kt b/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiModels.kt
new file mode 100644
index 000000000..59fc77caf
--- /dev/null
+++ b/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiModels.kt
@@ -0,0 +1,39 @@
+package eu.kanade.tachiyomi.extension.en.kouhaiwork
+
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class KouhaiSeries(
+    val id: Int,
+    val title: String,
+    val cover: String,
+    val synopsis: String,
+    val status: String,
+    val artists: List<String>,
+    val authors: List<String>,
+    val alternative_titles: List<String>,
+    val genres: List<String>? = null,
+    val themes: List<String>? = null,
+    val demographics: List<String>? = null,
+    val chapters: List<KouhaiChapter>
+)
+
+@Serializable
+data class KouhaiChapter(
+    val id: Int,
+    val group: String,
+    val number: Float,
+    val updated_at: String,
+    val name: String? = null
+)
+
+@Serializable
+data class KouhaiTag(val id: Int)
+
+@Serializable
+data class KouhaiTagList(
+    val genres: List<KouhaiTag>,
+    val themes: List<KouhaiTag>,
+    val demographics: List<KouhaiTag>,
+    val status: KouhaiTag?
+)
diff --git a/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiWork.kt b/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiWork.kt
new file mode 100644
index 000000000..18e4f628a
--- /dev/null
+++ b/src/en/kouhaiwork/src/eu/kanade/tachiyomi/extension/en/kouhaiwork/KouhaiWork.kt
@@ -0,0 +1,151 @@
+package eu.kanade.tachiyomi.extension.en.kouhaiwork
+
+import eu.kanade.tachiyomi.network.GET
+import eu.kanade.tachiyomi.network.POST
+import eu.kanade.tachiyomi.network.asObservableSuccess
+import eu.kanade.tachiyomi.source.model.FilterList
+import eu.kanade.tachiyomi.source.model.MangasPage
+import eu.kanade.tachiyomi.source.model.Page
+import eu.kanade.tachiyomi.source.model.SChapter
+import eu.kanade.tachiyomi.source.model.SManga
+import eu.kanade.tachiyomi.source.online.HttpSource
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.decodeFromJsonElement
+import kotlinx.serialization.json.encodeToJsonElement
+import kotlinx.serialization.json.jsonArray
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
+import okhttp3.FormBody
+import okhttp3.Response
+import uy.kohesive.injekt.injectLazy
+import java.text.DecimalFormat
+import java.text.SimpleDateFormat
+import java.util.Locale
+
+class KouhaiWork : HttpSource() {
+    override val name = "Kouhai Scanlations"
+
+    override val baseUrl = "https://kouhai.work"
+
+    override val lang = "en"
+
+    override val supportsLatest = true
+
+    private val json by injectLazy<Json>()
+
+    override fun latestUpdatesRequest(page: Int) =
+        GET("$API_URL/manga/week", headers)
+
+    override fun latestUpdatesParse(response: Response) =
+        response.parse()["data"]?.jsonArray?.map {
+            val arr = it.jsonArray
+            SManga.create().apply {
+                url = arr[0].jsonPrimitive.content
+                title = arr[1].jsonPrimitive.content
+                thumbnail_url = arr.last().jsonPrimitive.content
+            }
+        }.let { MangasPage(it ?: emptyList(), false) }
+
+    override fun popularMangaRequest(page: Int) =
+        GET("$API_URL/manga/all", headers)
+
+    override fun popularMangaParse(response: Response) =
+        latestUpdatesParse(response)
+
+    override fun searchMangaRequest(page: Int, query: String, filters: FilterList) =
+        FormBody.Builder().add("search", query).add("tags", filters.json())
+            .let { POST("$API_URL/manga/search", headers, it.build()) }
+
+    override fun searchMangaParse(response: Response) =
+        latestUpdatesParse(response)
+
+    // Request the actual manga URL for the webview
+    override fun mangaDetailsRequest(manga: SManga) =
+        GET("$baseUrl/series/${manga.url}", headers)
+
+    override fun fetchMangaDetails(manga: SManga) =
+        client.newCall(chapterListRequest(manga)).asObservableSuccess().map {
+            val series = it.data<KouhaiSeries>()
+            manga.description = series.synopsis
+            manga.author = series.authors.joinToString()
+            manga.artist = series.artists.joinToString()
+            manga.genre = series.genres.orEmpty()
+                .plus(series.themes.orEmpty())
+                .plus(series.demographics.orEmpty())
+                .joinToString()
+            manga.status = when (series.status) {
+                "ongoing" -> SManga.ONGOING
+                "finished" -> SManga.COMPLETED
+                else -> SManga.UNKNOWN
+            }
+            manga.initialized = true
+            return@map manga
+        }!!
+
+    override fun chapterListRequest(manga: SManga) =
+        GET("$API_URL/mangas/${manga.url}", headers)
+
+    override fun chapterListParse(response: Response) =
+        response.data<KouhaiSeries>().chapters.map {
+            SChapter.create().apply {
+                url = it.id.toString()
+                scanlator = it.group
+                chapter_number = it.number
+                name = "Chapter ${decimalFormat.format(it.number)}" +
+                    if (it.name == null) "" else " - ${it.name}"
+                date_upload = dateFormat.parse(it.updated_at)?.time ?: 0L
+            }
+        }
+
+    override fun pageListRequest(chapter: SChapter) =
+        GET("$API_URL/chapters/${chapter.url}", headers)
+
+    override fun pageListParse(response: Response) =
+        response.parse()["chapter"]!!.jsonObject["pages"]!!
+            .jsonArray.mapIndexed { idx, obj ->
+                Page(idx, "", obj.jsonObject["media"]!!.jsonPrimitive.content)
+            }
+
+    override fun getFilterList() =
+        FilterList(GenresFilter(), ThemesFilter(), DemographicsFilter(), StatusFilter())
+
+    override fun mangaDetailsParse(response: Response) =
+        throw UnsupportedOperationException("Not used")
+
+    override fun imageUrlParse(response: Response) =
+        throw UnsupportedOperationException("Not used")
+
+    @Suppress("NOTHING_TO_INLINE")
+    private inline fun FilterList.json() =
+        json.encodeToJsonElement(
+            KouhaiTagList(
+                find<GenresFilter>()?.state?.filter { it.state }
+                    ?.map { KouhaiTag(it.id) } ?: emptyList(),
+                find<ThemesFilter>()?.state?.filter { it.state }
+                    ?.map { KouhaiTag(it.id) } ?: emptyList(),
+                find<DemographicsFilter>()?.state?.takeIf { it != 0 }
+                    ?.let { listOf(KouhaiTag(it)) } ?: emptyList(),
+                find<StatusFilter>()?.state?.takeIf { it != 0 }
+                    ?.let { KouhaiTag(it - 1) }
+            )
+        ).toString()
+
+    @Suppress("NOTHING_TO_INLINE")
+    private inline fun Response.parse() =
+        json.parseToJsonElement(body!!.string()).jsonObject
+
+    private inline fun <reified T> Response.data() =
+        json.decodeFromJsonElement<T>(parse()["data"]!!)
+
+    private inline fun <reified T> FilterList.find() = find { it is T } as? T
+
+    companion object {
+        private const val API_URL = "https://api.kouhai.work/v2"
+
+        private const val ISO_DATE = "yyyy-MM-dd'T'HH:mm:ss.SSSSSS'Z'"
+
+        private val dateFormat = SimpleDateFormat(ISO_DATE, Locale.ROOT)
+
+        private val decimalFormat = DecimalFormat("#.##")
+    }
+}