| Title | Year | Genre |
|---|---|---|
| Octagon Reversi | 2000 | Puzzle |
| Oh! Hajiki! | ???? | Puzzle |
| Oh! Hajiki! Final | 1990 | Puzzle |
| Oh! Pai | ???? | Puzzle |
| Ohootsuku Ni Kiyu | ???? | Adventure |
| Okumanchouja | ???? | Adventure |
| Olteus II | 1991 | Shooter |
| One-key Flying | ???? | Shooter |
| Oni Gokko 68 | ???? | Adventure |
| Ooedo Hanseiki | ???? | Puzzle |
| Ora Ora Ball | 1995 | Arcade |
| Ora-Shoot | 1996 | Shooter |
| Orange Iro No Biyaku | 1989 | Puzzle |
| Ossan No Dotsuki Game Special | ???? | Arcade |
| Othello Master | 1991 | Puzzle |
| Otoko Dama | 1999 | Shooter |
| Otoshite Pon | ???? | Puzzle |
| Otsukerumono No Tetsujin | 1996 | Shooter |
| Ouen no Uta | 2000 | Adventure |
| Ougon No Buta | ???? | Arcade |
| Over Driver | 1992 | Shooter |
| Overtake | ???? | F1 racing |
