Books Series Beginning with O
- Curious George
- My Next Life as a Villainess: All Routes Lead to Doom!
- Ohoka Echizen
- Ojamajo
- Ojarumaru
- Okasan to Issho
- Omae Umasodana
- Omoide no Marnie (When Marnie Was There)
- One Piece
- One Punch Man
- Onegai My Melody
- Online Game
- Only Yesterday
- Ookami kodomo no Ame to Yuki (Wolf Children)
- Orange Page
- Orient
- Orix Buffaloes
- Osen
- Oshi ga Budokan Ittekuretara Shinu
- Oshiri Tantei
- Osomatsu-san
- Ossan's Love
- Otome continue
- otona MUSE
- Seraph of the End
- The Royal Tutor (Oshitsu Kyoshi Haine)