diff --git a/src/ja/gaugaumonsterplus/build.gradle b/src/ja/gaugaumonsterplus/build.gradle
new file mode 100644
index 000000000..031e3a0b5
--- /dev/null
+++ b/src/ja/gaugaumonsterplus/build.gradle
@@ -0,0 +1,11 @@
+ext {
+    extName = "Gaugau Monster Plus"
+    extClass = ".GaugauMonsterPlus"
+    extVersionCode = 1
+}
+
+apply from: "$rootDir/common.gradle"
+
+dependencies {
+    implementation(project(":lib:speedbinb"))
+}
diff --git a/src/ja/gaugaumonsterplus/res/mipmap-hdpi/ic_launcher.png b/src/ja/gaugaumonsterplus/res/mipmap-hdpi/ic_launcher.png
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diff --git a/src/ja/gaugaumonsterplus/res/mipmap-xhdpi/ic_launcher.png b/src/ja/gaugaumonsterplus/res/mipmap-xhdpi/ic_launcher.png
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diff --git a/src/ja/gaugaumonsterplus/res/mipmap-xxxhdpi/ic_launcher.png b/src/ja/gaugaumonsterplus/res/mipmap-xxxhdpi/ic_launcher.png
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diff --git a/src/ja/gaugaumonsterplus/src/eu/kanade/tachiyomi/extension/ja/gaugaumonsterplus/GaugauMonsterPlus.kt b/src/ja/gaugaumonsterplus/src/eu/kanade/tachiyomi/extension/ja/gaugaumonsterplus/GaugauMonsterPlus.kt
new file mode 100644
index 000000000..45044e6af
--- /dev/null
+++ b/src/ja/gaugaumonsterplus/src/eu/kanade/tachiyomi/extension/ja/gaugaumonsterplus/GaugauMonsterPlus.kt
@@ -0,0 +1,282 @@
+package eu.kanade.tachiyomi.extension.ja.gaugaumonsterplus
+
+import eu.kanade.tachiyomi.lib.speedbinb.SpeedBinbInterceptor
+import eu.kanade.tachiyomi.lib.speedbinb.SpeedBinbReader
+import eu.kanade.tachiyomi.network.GET
+import eu.kanade.tachiyomi.source.model.Filter
+import eu.kanade.tachiyomi.source.model.FilterList
+import eu.kanade.tachiyomi.source.model.SChapter
+import eu.kanade.tachiyomi.source.model.SManga
+import eu.kanade.tachiyomi.source.online.ParsedHttpSource
+import kotlinx.serialization.json.Json
+import okhttp3.HttpUrl.Companion.toHttpUrl
+import okhttp3.Request
+import org.jsoup.nodes.Document
+import org.jsoup.nodes.Element
+import uy.kohesive.injekt.Injekt
+import uy.kohesive.injekt.api.get
+
+class GaugauMonsterPlus : ParsedHttpSource() {
+
+    override val name = "がうがうモンスター＋"
+
+    override val baseUrl = "https://gaugau.futabanet.jp"
+
+    override val lang = "ja"
+
+    override val supportsLatest = false
+
+    private val json = Injekt.get<Json>()
+
+    override val client = network.client.newBuilder()
+        .addInterceptor(SpeedBinbInterceptor(json))
+        .build()
+
+    override fun headersBuilder() = super.headersBuilder()
+        .add("Referer", "$baseUrl/")
+
+    override fun popularMangaRequest(page: Int) = GET("$baseUrl/list/works?page=$page", headers)
+
+    override fun popularMangaSelector() = ".works__grid .list__box"
+
+    override fun popularMangaFromElement(element: Element) = SManga.create().apply {
+        element.selectFirst("h4 a")!!.let {
+            setUrlWithoutDomain(it.attr("href"))
+            title = it.text()
+        }
+        author = element.select(".list__text span a").joinToString { it.text() }
+        genre = element.select(".tag__item").joinToString { it.text() }
+        thumbnail_url = element.selectFirst(".thumbnail .img-books")?.absUrl("src")
+    }
+
+    override fun popularMangaNextPageSelector() = "ol.pagination li.next a:not([href='#'])"
+
+    override fun latestUpdatesRequest(page: Int) = throw UnsupportedOperationException()
+
+    override fun latestUpdatesSelector() = throw UnsupportedOperationException()
+
+    override fun latestUpdatesFromElement(element: Element) = throw UnsupportedOperationException()
+
+    override fun latestUpdatesNextPageSelector() = throw UnsupportedOperationException()
+
+    override fun searchMangaRequest(page: Int, query: String, filters: FilterList): Request {
+        val tagFilter = filters.ifEmpty { getFilterList() }.filterIsInstance<TagFilter>().first()
+        val url = baseUrl.toHttpUrl().newBuilder().apply {
+            if (query.isNotEmpty()) {
+                addPathSegments("list/search-result")
+                addQueryParameter("word", query)
+            } else if (tagFilter.state != 0) {
+                addPathSegments("list/tag")
+                addPathSegment(tagFilter.values[tagFilter.state])
+            } else {
+                addPathSegment("list/works")
+            }
+
+            if (page > 1) {
+                addQueryParameter("page", page.toString())
+            }
+        }.build()
+
+        return GET(url, headers)
+    }
+
+    override fun searchMangaSelector() = popularMangaSelector()
+
+    override fun searchMangaFromElement(element: Element) = popularMangaFromElement(element)
+
+    override fun searchMangaNextPageSelector() = popularMangaNextPageSelector()
+
+    override fun mangaDetailsParse(document: Document) = SManga.create().apply {
+        title = document.selectFirst(".mbOff h1")!!.text()
+        author = document.select(".list__text span a").joinToString { it.text() }
+        description = document.selectFirst("p.mbOff")?.text()
+        genre = document.select(".tag__item").joinToString { it.text() }
+        thumbnail_url = document.selectFirst(".list__box .thumbnail .img-books")?.absUrl("src")
+    }
+
+    override fun chapterListRequest(manga: SManga) = GET("$baseUrl${manga.url}/episodes", headers)
+
+    override fun chapterListSelector() =
+        "#episodes .episode__grid:not(:has(.episode__button-app, .episode__button-complete)) a"
+
+    override fun chapterFromElement(element: Element) = SChapter.create().apply {
+        val episodeNum = element.selectFirst(".episode__num")!!.text()
+        val episodeTitle = element.selectFirst(".episode__title")?.text()
+            ?.takeIf { t -> t.isNotBlank() }
+
+        setUrlWithoutDomain(element.attr("href"))
+        name = buildString(episodeNum.length + 2 + (episodeTitle?.length ?: 0)) {
+            append(episodeNum)
+
+            if (episodeTitle != null) {
+                append("「")
+                append(episodeTitle)
+                append("」")
+            }
+        }
+        // There is actually a consistent chapter number format on this site, which we
+        // take advantage of because the built-in chapter number parser doesn't properly
+        // parse the fractions.
+        chapter_number = CHAPTER_NUMBER_REGEX.matchEntire(episodeNum)?.let { m ->
+            val major = m.groupValues[1].toFloat()
+            val minor = m.groupValues[2].toFloat()
+
+            major + minor / 10
+        } ?: -1F
+    }
+
+    private val reader by lazy { SpeedBinbReader(client, headers, json) }
+
+    override fun pageListParse(document: Document) = reader.pageListParse(document)
+
+    override fun imageUrlParse(document: Document) = throw UnsupportedOperationException()
+
+    override fun getFilterList() = FilterList(
+        Filter.Header("フリーワード検索はジャンル検索では機能しません"),
+        TagFilter(),
+    )
+}
+
+private val CHAPTER_NUMBER_REGEX = Regex("""^第(\d+)話\((\d+)\)$""")
+
+// https://gaugau.futabanet.jp/list/search
+// copy([...document.querySelectorAll(".tagSearch__item")].map((e) => `"${e.textContent.trim()}",`).join("\n"))
+private class TagFilter : Filter.Select<String>(
+    "ジャンル",
+    arrayOf(
+        "なし",
+        "転生・召喚",
+        "少年向け",
+        "青年向け",
+        "大人向け",
+        "少女向け",
+        "追放",
+        "女性向け",
+        "チート",
+        "もふもふ",
+        "小説",
+        "スローライフ",
+        "時代物",
+        "異世界転生",
+        "官能",
+        "歴史",
+        "ライトノベル",
+        "婚約破棄",
+        "暮らし",
+        "料理",
+        "結婚",
+        "医療",
+        "恋",
+        "溺愛",
+        "教養",
+        "ミリタリー",
+        "逆ハーレム",
+        "戦争",
+        "寝取られ",
+        "おっぱい",
+        "趣味",
+        "巨乳",
+        "ファッション",
+        "グルメ",
+        "TS",
+        "最強",
+        "天才",
+        "勇者",
+        "癒し",
+        "魔王",
+        "雑学",
+        "女主人公",
+        "成り上がり",
+        "探偵",
+        "引きこもり",
+        "社畜",
+        "ツンデレ",
+        "子育て",
+        "ヤンデレ",
+        "絵本",
+        "青年",
+        "女性",
+        "少女",
+        "少年",
+        "アウトドア",
+        "おっさん",
+        "スポーツ",
+        "トレーニング",
+        "幼馴染",
+        "同級生",
+        "ダイエット",
+        "高校生",
+        "令嬢",
+        "美少女",
+        "エッセイ",
+        "美人",
+        "妹",
+        "貴族",
+        "イケメン",
+        "ヒューマンドラマ",
+        "双子",
+        "冒険",
+        "魔法",
+        "4コマ",
+        "魔女",
+        "ショートショート",
+        "サキュバス",
+        "スライム",
+        "エルフ",
+        "ヤンキー",
+        "ギャンブル",
+        "獣人",
+        "サブカル",
+        "ミステリー",
+        "乙女ゲーム",
+        "サスペンス",
+        "シリアス",
+        "ホラー",
+        "ラブコメ",
+        "恋愛",
+        "胸キュン",
+        "いじめ",
+        "アクション",
+        "サバイバル",
+        "バトル",
+        "絶望",
+        "アニメ",
+        "ギャグ",
+        "動物",
+        "猫",
+        "非異世界",
+        "百合",
+        "内政",
+        "BL",
+        "ダンジョン",
+        "幼なじみ",
+        "田舎",
+        "学園",
+        "悪役令嬢",
+        "なろう",
+        "異世界",
+        "メディアミックス",
+        "ファンタジー",
+        "お仕事もの",
+        "人外",
+        "オフィスラブ",
+        "日常",
+        "夫婦",
+        "家族",
+        "アラサー",
+        "アラフォー",
+        "中高年",
+        "老後",
+        "話題",
+        "重版",
+        "音楽",
+        "幕末",
+        "お金",
+        "長期連載",
+        "読み切り",
+        "1話完結",
+        "ゲーム",
+        "人情",
+        "ハーレム",
+    ),
+)