diff --git a/internal/episodes/service/merge.go b/internal/episodes/service/merge.go
new file mode 100644
index 0000000..fdf56f0
--- /dev/null
+++ b/internal/episodes/service/merge.go
@@ -0,0 +1,133 @@
+package service
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+
+	"mal/integrations/jikan"
+	"mal/internal/domain"
+)
+
+type episodePartial struct {
+	title  string
+	filler bool
+	recap  bool
+	sub    bool
+	dub    bool
+}
+
+func titleCandidates(anime domain.Anime) []string {
+	out := []string{anime.Title}
+	if anime.TitleEnglish != "" && anime.TitleEnglish != anime.Title {
+		out = append(out, anime.TitleEnglish)
+	}
+	if anime.TitleJapanese != "" {
+		out = append(out, anime.TitleJapanese)
+	}
+	for _, syn := range anime.TitleSynonyms {
+		if syn != "" && syn != anime.Title && syn != anime.TitleEnglish && syn != anime.TitleJapanese {
+			out = append(out, syn)
+		}
+	}
+	return out
+}
+
+func isCanonicalEpisodePayloadValid(payload domain.CanonicalEpisodeList, expectedCount int) bool {
+	if expectedCount <= 0 {
+		return true
+	}
+	if len(payload.Episodes) > expectedCount {
+		return false
+	}
+	for _, episode := range payload.Episodes {
+		if episode.Number <= 0 || episode.Number > expectedCount {
+			return false
+		}
+	}
+	return true
+}
+
+func mergeEpisodes(jikanEpisodes []jikan.Episode, availability domain.EpisodeAvailability, expectedCount int) []domain.CanonicalEpisode {
+	byNumber := map[int]episodePartial{}
+
+	for i, ep := range jikanEpisodes {
+		if exceedsExpectedCount(i+1, expectedCount) {
+			break
+		}
+		number, ok := jikanEpisodeNumber(ep, i)
+		if !ok || exceedsExpectedCount(number, expectedCount) {
+			continue
+		}
+		mergeEpisode(&byNumber, number, func(item *episodePartial) {
+			item.title = strings.TrimSpace(ep.Title)
+			item.filler = ep.Filler
+			item.recap = ep.Recap
+		})
+	}
+	mergeAvailability(&byNumber, availability.Sub, expectedCount, func(item *episodePartial) { item.sub = true })
+	mergeAvailability(&byNumber, availability.Dub, expectedCount, func(item *episodePartial) { item.dub = true })
+
+	numbers := make([]int, 0, len(byNumber))
+	for number := range byNumber {
+		numbers = append(numbers, number)
+	}
+	sort.Ints(numbers)
+
+	episodes := make([]domain.CanonicalEpisode, 0, len(numbers))
+	for _, number := range numbers {
+		item := byNumber[number]
+		title := item.title
+		if title == "" {
+			title = fmt.Sprintf("Episode %d", number)
+		}
+		episodes = append(episodes, domain.CanonicalEpisode{
+			Number:  number,
+			Title:   title,
+			HasSub:  item.sub,
+			HasDub:  item.dub,
+			SubOnly: item.sub && !item.dub,
+			Filler:  item.filler,
+			Recap:   item.recap,
+		})
+	}
+	return episodes
+}
+
+func mergeEpisode(byNumber *map[int]episodePartial, number int, update func(*episodePartial)) {
+	item := (*byNumber)[number]
+	update(&item)
+	(*byNumber)[number] = item
+}
+
+func mergeAvailability(byNumber *map[int]episodePartial, numbers []int, expectedCount int, update func(*episodePartial)) {
+	for _, number := range numbers {
+		if number <= 0 || exceedsExpectedCount(number, expectedCount) {
+			continue
+		}
+		mergeEpisode(byNumber, number, update)
+	}
+}
+
+func jikanEpisodeNumber(ep jikan.Episode, index int) (int, bool) {
+	number, err := strconv.Atoi(strings.TrimSpace(ep.Episode))
+	if err == nil && number > 0 {
+		return number, true
+	}
+	if index < 0 {
+		return 0, false
+	}
+	return index + 1, true
+}
+
+func exceedsExpectedCount(number int, expectedCount int) bool {
+	return expectedCount > 0 && number > expectedCount
+}
+
+func truncate(value string, maxLen int) string {
+	if len(value) <= maxLen {
+		return value
+	}
+	return value[:maxLen]
+}