Magazine Series Beginning with O
- [Oshi no ko]
- Curious George
- My Next Life as a Villainess: All Routes Lead to Doom!
- Obey Me!
- Occultic;Nine
- Ochikobore Fruits Tarte
- Ochoyan
- Octave
- OCTOPATH TRAVELER
- Oda Nobuna no Yabou
- Odoru Daisosasen Series
- Oh-oku ( Danjo Gyakuten)
- Ohoka Echizen
- Oishinbo
- Ojamajo
- Oka-san Musume wo Yameteiidesuka?
- Okaeri Mone
- Okami Shojo to Kuro Oji
- Okami to Koshinryo (Wolf and Spice)
- Okasan to Issho
- Okiku Furikabutte
- Okusama ga Seito Kaicho!
- Okusama wa Toriatsukaichui
- Olympia Cuculus
- Olympic
- Omamori Himari
- Omoi, Omoware, Furi, Furare
- Omoide no Marnie (When Marnie Was There)
- Omukaedesu.
- One Piece
- One Punch Man
- Oneechan ga Kita
- Onegai My Melody
- Onegai Teacher (Please Teacher!)
- Ongaku to Hito
- Onichan Dakedo Ai Sae Areba Kankeinaiyone
- Onihei Hankacho
- Onimai: I'm Now Your Sister!
- Onimusha
- Online Game
- Only Mercedes
- Only Yesterday
- Onna Joshu Naotora
- Onna no Sono no Hoshi
- Onnamichi
- Ooi! Tombo
- Ookami kodomo no Ame to Yuki (Wolf Children)
- Ookami-san Series
- Ooya-san wa Shishunki !
- Opanchu Usagi
- orange
- Orange Page
- Ore Ga Sukina No Ha Imotodakedo Imoto Janai
- Ore monogatari!!
- Ore no Imoto ga Kon nani Kawaii wake ga nai
- Ore no Kanojo to Osananajimi ga Shuraba Sugiru
- Ore no Sora Series
- Ore o Suki nano wa Omae dake kayo
- Ore, Twintail ni Narimasu.
- Orenchi no Furo Jijyo
- Ori Sta
- Orient
- Orix Buffaloes
- Osama Game
- Osama Ranking
- Osananajimi ga zettai ni makenai love-come
- Osen
- Oshi ga Budokan Ittekuretara Shinu
- Oshiri Tantei
- Osomatsu-san
- Ossan's Love
- Otaku Elf
- Otaku ni Koi wa Muzukashii
- Otenki One-san
- Otherside PIcnic
- Otoca Doll
- Otoko wa Tsuraiyo
- Otokomeshi
- Otome Yokai Zakuro
- otona MUSE
- Otona no Natsuyasumi
- Otona no Oshare Techo
- Ougon no Gt
- Our Dearest Sakura (Doki no Sakura)
- Ouran Koko Host Club
- Ouroboros
- Outbreak Company
- Overlord
- Overtake!
- Oyuki Umi no Kina
- Please Tell Me! Galko-chan
- Seraph of the End
- Shomin Sample
- The Royal Tutor (Oshitsu Kyoshi Haine)
- Uncle from Another World