# 1998 Japan Open Tennis Championships – Women's singles

First-seeded Ai Sugiyama was the defending champion and won in the final 6–3, 6–3 against Corina Morariu.

## Seeds

A champion seed is indicated in bold text while text in italics indicates the round in which that seed was eliminated. The top two seeds received a bye to the second round.
* Ai Sugiyama (champion)
* Naoko Sawamatsu (quarterfinals)
* Tamarine Tanasugarn (second round)
* Amy Frazier (semifinals)
* Corina Morariu (final)
* Shi-Ting Wang (semifinals)
* Miho Saeki (first round)
* Yuka Yoshida (second round)

## Draw
### Key

* Q = Qualifier
* WC = Wild card
* LL = Lucky loser
* Alt = Alternate
* SE = Special exempt
* PR = Protected ranking
* ITF = ITF entry
* JE = Junior exempt
* w/o = Walkover
* r = Retired
* d = Defaulted
* SR = Special ranking

### Final

| Final | Final | Final | Final | Final |
| 1 | Ai Sugiyama | 6 | 6 | |
| 5 | Corina Morariu | 3 | 3 | |

### Section 1

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| | | | | | 1 | A Sugiyama | 6 | 6 | | | | | | | | | | |
| | N Miyagi | 6 | 3 | 7 | | S-T Wang | 3 | 2 | | | | | | | | | | |
| | L Osterloh | 0 | 6 | 6 | | | | | | 1 | A Sugiyama | 4 | 6 | 6 | | | | |
| Q | S De Beer | 4 | 4 | | | | | | | | E deLone | 6 | 1 | 1 | | | | |
| | E deLone | 6 | 6 | | | E deLone | 6 | 2 | 6 | | | | | | | | | |
| | N Kijimuta | 1 | 6 | 1 | 8 | Y Yoshida | 3 | 6 | 2 | | | | | | | | | |
| 8 | Y Yoshida | 6 | 4 | 6 | | | | | | | | | | | 1 | A Sugiyama | 6 | 6 |
| 3 | T Tanasugarn | 4 | 7 | 6 | | | | | | | | | | | 6 | S-T Wang | 3 | 2 |
| | E-H Kim | 6 | 5 | 0 | 3 | T Tanasugarn | 2 | 3 | | | | | | | | | | |
| | M-R Jeon | 4 | 1 | | | L McNeil | 6 | 6 | | | | | | | | | | |
| | L McNeil | 6 | 6 | | | | | | | | L McNeil | 6 | 4 | 1 | | | | |
| Q | S Hisamatsu | 2 | 2 | | | | | | | 6 | S-T Wang | 4 | 6 | 6 | | | | |
| | R Hiraki | 6 | 6 | | | R Hiraki | 3 | 2 | | | | | | | | | | |
| WC | S Asagoe | 6 | 3 | 1 | 6 | S-T Wang | 6 | 6 | | | | | | | | | | |
| 6 | S-T Wang | 3 | 6 | 6 | | | | | | | | | | | | | | |

### Section 2

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 7 | M Saeki | 6 | 2 | | | | | | | | | | | | | | | | |
| | G Helgeson-Nielsen | 7 | 6 | | | G Helgeson-Nielsen | 3 | 2 | | | | | | | | | | | |
| WC | S Obata | 5 | 1 | | | N Pratt | 6 | 6 | | | | | | | | | | | |
| | N Pratt | 7 | 6 | | | | | | | | N Pratt | 2 | 6 | 2 | | | | | |
| | K Kunce | 7 | 4 | 1 | | | | | | 4 | A Frazier | 6 | 4 | 6 | | | | | |
| Q | M Endo | 6 | 6 | 6 | Q | M Endo | 0 | 1 | | | | | | | | | | | |
| Q | Y-J Choi | 4 | 2 | | 4 | A Frazier | 6 | 6 | | | | | | | | | | | |
| 4 | A Frazier | 6 | 6 | | | | | | | | | | | | 4 | A Frazier | 6 | 6 | 4 |
| 5 | C Morariu | 6 | 6 | | | | | | | | | | | | 5 | C Morariu | 4 | 7 | 6 |
| | S-H Park | 4 | 2 | | 5 | C Morariu | 6 | 6 | | | | | | | | | | | |
| | M Shaughnessy | 3 | 6 | 6 | | M Shaughnessy | 3 | 2 | | | | | | | | | | | |
| | J Lee | 6 | 2 | 4 | | | | | | 5 | C Morariu | 7 | 6 | | | | | | |
| | H Inoue | 6 | 6 | | | | | | | 2 | N Sawamatsu | 5 | 3 | | | | | | |
| | S Noorlander | 4 | 1 | | | H Inoue | 6 | 4 | 6 | | | | | | | | | | |
| | | | | | 2 | N Sawamatsu | 4 | 6 | 7 | | | | | | | | | | |