| Osananajimi ga Ore o Okazu ni Jii Shimakutteita Ken ~Jibaku Shumi no Do Hentai Deshita~ | 2022-12-02 | 5.90 (6) |
| Osananajimi ga Dosukebe Kawaii | 2018-08-25 | - (4) |
| Osananajimi ga Chichioya to Dekiteita Ken ni Tsuite ~Oyaji kara no Shuuchi Netori Choukyou~ | 2016-04-01 | 6.50 (32) |
| Osananajimi Yori mo Eroi Mobko to no Houkago Ecchi ~Boku wa Class no Jimiko ni Koi o Shita~ | 2023-02-03 | 6.30 (17) |
| Osananajimi Ojou-sama to H de Himitsu na Dousei Seikatsu | 2023-07-28 | 6.40 (29) |
| Osananajimi DAYS ~Anna to kurasu 14-nich~ | 2023-10-14 | 6.40 (13) |
| Osananajimi Childhood Love | 2024-05-27 | 6.00 (12) |
| Osananajimi 2 | 1999-12-26 | - (2) |
| Osananajimi | 1997-12-29 | - (2) |
| Osananajimi | 2002-10-04 | - (4) |
| Osananajimi | 2000-10-13 | - (1) |
| Osanai Lemon to Otona no Vanilla | 2026-04-27 | - (3) |
| Osanai Imouto no Sei Nikki ~Natsumi to Haruna~ | 2004-11 | - |
| Osanai Imouto no Sei Nikki ~Anna to Ichigo~ | 2005-06-12 | - |
| Osanahime | 2006-06-22 | - |
| Osanagokoro no Kimi ~Akumu no Juukan Choukyou~ | 2007-05-23 | - |
| Osana na Jiri ~Gimic LOw mizu~ | 2012-02-10 | - (3) |
| Osakon ~Osananajimi to Icha Love Kekkon Katsudou~ | 2011-06-24 | 5.70 (13) |
| Osakoi ~Ore to Futari no Ama Ama Gohoushi H Seikatsu~ | 2016-02-26 | 6.40 (22) |
| Osaka Teikoku Eiyuu-tachi. ~Yodogawa Yori mo Nagaku Kimi o Aisu~ | 2016-09-28 | - (1) |
| Osaka Teikoku Danshi. ~Hanwasen wa Tomatte mo Koi wa Nonstop!~ | 2016-09-03 | - (1) |
| Osaka Gitai Yu | 2024-08-12 | - (1) |
| Osaka Crisis ~Kanrakugai Kaihatsu Project~ | 2009-03-27 | 7.20 (60) |
| Osaka Awaking | 2017-09-29 | 7.40 (42) |
| Osagena Boku no Onnanoko | 2006-01-18 | - (1) |
| Osadere! | 2009-11-07 | - (1) |
| Orwell: Keeping an Eye On You | 2016-10-27 | 7.00 (143) |
| Orwell: Ignorance is Strength | - | 6.30 (23) |
| Orveia | 2023-08-13 | - (1) |
| Orthros 3rd Title | - | - |
| Orpheus | 2013-02-28 | - (2) |
| Orphan and the Lost Mother | - | - |
| Ornithogalum no Hakoniwa | - | - |
| Orly Kuukou Satsujin Jiken | 1983-11 | - (1) |
| Oriunten wo Gekitai Suru Tatta Hitotsu no Houhou | 2025-10-24 | - |
| Orion the Oracle | 2026-01-21 | - |
| Orion Heart ~Injoku no Suku Mizu Sailor Senshi~ | 2009-03-27 | 5.00 (227) |
| Orion | 2015-09-28 | 5.60 (32) |
| Orion | - | - |
| Orihime ~Gokujou no Mirai wa Ore no Mono~ | 2021-02-26 | 6.70 (57) |
| Orihime Yuna ~Tsunagareta Futari no Seijo~ | 2008-01-12 | - |
| Origoshino, | 2010-08-27 | - (4) |
| Original Ehon "Sono Saki to" | 2018-03-21 | - |
| Origin Story | 2025-09-30 | 7.00 (13) |
| Origin | 2024-09-29 | - |
| Origamo Furioso | - | 5.40 (5) |
| Origami Tsuki | 2014 | - (1) |
| Origami Solutions | - | - |
| Orient on the Murder Express | 2024-05-15 | - |
| Oriakos | 2024-07-23 | - |