Illustrator Takumi Yokooka said that Katsutoshi Fujioka was one of his staff members in the late 80s - early 90s, when both artists worked frequently with Namco. (Source: mentioned by Namco historian Zekuu)
Games
Other video game related works
Gallery part 1
Gallery part 2
Algarna / アルガーナ (X68000 - 1991)
Main visual (Source: credited in the calendar from the November 1990 issue of Technopolis)
Battle Cross / バトルクロス (SFC - 1994)
Cover art (Source: credited on the cover)
Break Volley / ブレイクバレー (PS1 - 1999)
Character illustrations (Source: mentioned on the artist's website)
Choro Q Park / チョロQパーク (Saturn - 1998)
Cover art (Source: mentioned on the artist's website)
Cross Hunter / クロスハンター (GBC - 2000)
? (Source: mentioned on the artist's old website (picture(s) not available))
Dragon Egg! / どらごんEGG！ (PC Engine - 1991)
Cover art / promotional illustration (Source: credited on a paper ad)
Drakan - Order of the Flame / ドラカン オーダー オブ ザ フレイム ~炎の騎士団~ (Windows - 1999)
Cover art for the Japanese version (Source: mentioned on the artist's website)
Hanjuku Hero / 半熟英雄 (Famicom - 1988)
Cover art (Source: credited on a paper ad featured in the January 6, 1989 issue of Famitsu)
Hanjuku Hero: Aa, Sekaiyo Hanjukunare...! / 半熟英雄 ああ、世界よ半熟なれ…!! (SFC - 1992)
Promotional illustration (Source: mentioned on the artist's old website)
Ide Meijin no Mahjong Kyōshitsu / 井出名人の麻雀教室 (PS1, GBC - 1999)
Character illustrations (Source: mentioned on the artist's website)
KickBall / キックボール (PC Engine - 1990)
? (Source: mentioned on the artist's old website (picture(s) not available))
King of Producer / キングオブプロデューサー (PS1 - 1996)
Cover art (Source: credited on a paper ad)
Logo design (Source: mentioned on the artist's website)
Makai Tōshi Sa・Ga / 魔界塔士Sa・Ga, AKA The Final Fantasy Legend (Game Boy - 1989)
Cover art for the Japanese version (Source: credited on Square Enix's website)
Medarot 3 / メダロット 3 (GBC - 2000)
Logo design (Source: mentioned on the artist's website)
Medarot R / メダロットR (PS1 - 1999)
Logo design (Source: mentioned on the artist's website)
Medarot R - Parts Collection / メダロットR パーツコレクション (PS1 - 2000)
Logo design (Source: mentioned on the artist's website)
Moto Roader MC / モトローダーMC (PC Engine CD - 1992)
? (Source: mentioned on the artist's old website (picture(s) not available))
Navy Blue / ネイビーブルー (Famicom - 1992)
Cover art (Source: mentioned on the artist's old website (picture(s) not available))
Network Adventure Bugsite / ネットワーク冒険記バグサイト (GBC - 2001)
Logo design (katakana version) (Source: mentioned on the artist's website)
Nounai Aesthe IQ Suppli DS 2 - Sukkiri King Kettei / 脳内エステ IQサプリDS2 -スッキリキング決定戦- (DS - 2007)
Character design (Source: mentioned on the artist's website)
Parlor Station / パーラーステーション (PS1 - 1998)
Logo design (Source: mentioned on the artist's website)
Pi to Mail / pi と メール (PS1 - 1999)
Cover art (Source: mentioned on the artist's website)
Sa・Ga 2: Hihō Densetsu / サガ2秘宝伝説, AKA Final Fantasy Legend II (Game Boy - 1990)
Cover art for the Japanese version (Source: credited on Square Enix's website)
Sa・Ga 3: Jikū no Hasha / サガ3時空の覇者, AKA Final Fantasy Legend III (Game Boy - 1991)
Cover art for the Japanese version (Source: credited on Square Enix's website)
SaGa Collection / サガ コレクション, AKA Collection of SaGa: Final Fantasy Legend (Switch - 2020)
Main illustration (Source: credited in an article published by Famitsu)
Sanrio Time Net: Kako-hen / サンリオタイムネット 過去編 (GBC - 1998)
Back cover (Source: mentioned on the artist's website)
SimCity Jr. / シムシティJr. (SFC - 1996)
Cover art (Source: credited on the back of the box)
Space-Net: Cosmo Neo / スペースネットコスモネオ (GBC - ~2001 - unreleased)
Logo design (Source: mentioned on the artist's website)
Square's Tom Sawyer / スクウェアのトム・ソーヤ (Famicom - 1989)
Cover art, illustrations (Source: credited on the back of the box)
Sumo Fighter: Tōkaidō Basho / 相撲ファイター 東海道場所 (Game Boy - 1991)
? (Source: mentioned on the artist's old website (picture(s) not available))
Super Kick Off / スーパーキックオフ (SFC - 1992)
Manual illustrations for the Japanese version (Source: credited in the manual)
The Heiwa Otenki Studio / The Heiwa お天気スタジオ (PS1 - 2001)
Character illustrations (Source: mentioned on the artist's website: 1, 2)
The Mystic Dragoons / ミスティック・ドラグーン (PS1 - 1999)
Logo design (Source: mentioned on the artist's website)
Vixen 357 / ヴィクセン357 (Mega Drive - 1992)
Character design (Source: in-game credits)
Waku Waku Volley / わくわくバレー (PS1 - 1998)
Cover art, character illustrations (Source: mentioned on the artist's website)
Wing Island / ウィングアイランド (Wii - 2006)
Cover art for the Japanese and European versions (Source: mentioned on the artist's website)
Wolf Fang SS Kūga 2001 / ウルフファング・ＳＳ 空牙２００１ (PS1 - 1996, Saturn - 1997)
"Illustration" (Source: in-game credits)
World Class Rugby 2 / ワールドクラスラグビー2 (SFC - 1994)
Cover art (Source: mentioned on the artist's old website)
Live A Live Kanzen Kōryaku Guide Book / ライブ・ア・ライブ完全攻略ガイドブック (book - 1994)
Illustrations (Source: credited in the book)
Marukatsu Game Shōnen / マル勝ゲーム少年 (magazine)
Cover art (Source: mentioned on the artist's website)
Namco Game Sound Express VOL.2 Burning Force / ナムコ ゲーム サウンド エクスプレス VOL.2 バーニングフォース (OST - 1990)
Cover art (Source: credited in the october 1989 issue of Namco NG)
.Note: the cover art war originally created for the cover of the october 1989 issue of Namco NG
Namco NG #28-33, 35-37, 39-43, 45-47 (magazine - 1989-1992)
Cover art (Source: credited in each issue)
SaGa 1・2・3 Original Soundtack Revival Disc (OST - 2018)
Cover art (Source: credited on Square Enix's website)