The designers at the time created both Mature and Vice with the image of a "ruthless woman" and a "cruel woman" respectively. Their origin story was mostly based on the notion of Rugal employing secretaries prior to The King of Fighters '96. Both women were unavailable during location testing and were likely finished near the end of the game's production schedule.  
One of the Hakkesshu, Mature joins forces with Vice to serve her master, Orochi. She often takes orders from Leopold Goenitz, although she doesn't like him. She and Vice were ordered to keep an eye on Rugal Bernstein, who was trying to use Orochi's power. They posed as his secretaries.
When Rugal died, Goenitz ordered Vice and Mature to keep an eye on Iori Yagami and bring him to the 1996 tournament. They didn't win the tournament, but when Kyo Kusanagi and Iori defeated Goenitz, Iori entered the Riot of the Blood and killed Vice and Mature. Although dead, both women continue to haunt Iori as shadows to entertain themselves.
Tales of Ash
Not knowing why they still exist, she and Vice tempt Iori to enter the newest tournament and volunteer to be his teammates once more. The women want to prevent Orochi's power from being stolen by Ash or Those from the Past. She looks forward to seeing him fight without his flames.
After the climax of the KOF XIII tournament, Iori's magatama returns to his possession and the weakened Orochi seal begins to strengthen itself once more. Both she and Vice ask if he truly wants to accept the magatama and the Orochi blood once more, offering him a final chance to completely eradicate the cursed fate from his bloodline. When Iori refuses their offer, the women fade once more out of existence. They state they will meet him again in his dreams.
Mature and Vice return once more while Iori visits a grave. Vice tosses him an invitation to KOF, she mentions that this KOF is just the beginning of the nightmare. Just like in the previous tournament, Mature looks forward to seeing Iori fight with his flames.
After the climax of the tournament, Mature and Vice don't stop Iori who was going to seal Orochi. She states that all destinies are beginning to shift, with Vice agreeing, she comments that Iori can't resist his blood once it boils. The women return to the dead once more.
In contrast of Vice, Mature is ruthless but she likes to toy with her victim a little bit, often using her charms. She seemed to have liked Rugal while they were together. Though Iori killed both of them and continued to be hostile to them as phantoms, she and Vice seem genuinely concerned for Iori's well being and respect his wishes, despite clearly being an enemy of theirs. Their dislike of Goenitz implied that they are uninterested in the affairs of the Hakkeshu and in connection, the Orochi as well.
Mature is bisexual .
- Slashing Hands - Her hands can slash and pierce as if they were knives.
- Cutting Attacks - Mature can infuse her hand strikes with cutting energy.
- Cutting Projectile - Mature can create a projectile made of cutting energy.
- Snake Arms - Mature can stretch her arms in front of her within a long range and with high speed (But it is not as fast as Vice's Snake Arms).
- Negative Energy - Mature can slam a foe out of pure hatred, producing a pillar of dim light with a large skull inside, this attribute sometimes manifests itself in a burst of deep crimson as well.
- Knife Nails - Mature has pink, sharp, acrylic nails, most likely used to cut and slash.
- Hakkeshu: Light - The powers of light grant Mature fast reflexes and movements, along with enhanced speed.
- Solid Illusion Image - Mature can make a copy of herself to assist in slashing for a short period of time.
- Lipstick Trail - Mature can leave a trace of on her lipstick when moving fast, as evidenced in her KOF XIV Climax DM.
Her fighting style focuses on speed and using her cutting powers. She has some acrobatic maneuvers as well.
- Hiroko Tsuji - The King of Fighters '96~XIII
- Keiko Tsutsui - The King of Fighters XIV
- Yū Shimamura - The King of Fighters World~Destiny
- Yuki Sakura - King of Fighters movie (Japanese voice)
Live Action Actors
- Monique Ganderton - The King of Fighters movie
- Arashi no Saxophone - The King of Fighters XIII (when the music is set to "Type B", console version only, shared with Iori Yagami and Vice)
- Arashi no Saxophone 2 - The King of Fighters '96, '98 and 2002
- Arashi no Saxaphone 5 - The King of Fighters XIII
- Saxophone Under the Moon - The King of Fighters XIV
- Tranquilizer - The King of Fighters 2002 Unlimited Match
- The King of Fighters '96
- The King of Fighters '98
- The King of Fighters '98 Ultimate Match
- The King of Fighters 2000 - As a Striker for Iori alongside Vice
- The King of Fighters 2002
- The King of Fighters 2002 Unlimited Match
- The King of Fighters Neowave
- The King of Fighters XII (home version)
- The King of Fighters XIII
- CR The King of Fighters
- The King of Fighters XIV
- Days of Memories (second title) - unplayable
- SNK Gals Rhythm Combo Yudanshinaide!
- SNK Highschool Collection
- The King of Fighters '98 Ultimate Match Online
- Metal Slug Defense (unlockable)
- Kimi wa Hero
- The King of Fighters Destiny
- The King of Fighters World
- The King of Fighters All Star
- SNK All Star
- The King of Fighters '94 - during in-game cutscenes
- The King of Fighters '97 - in the Hero team's ending
- The King of Fighters 2003 - during the edit team ending
- The King of Fighters XI - background cameo in PS2 port
- KOF: Maximum Impact 2 - background cameo
- The King of Fighters '94: Rebout - background cameo in the Kim Team stage
- Garou: Mark of the Wolves - in Hokutomaru's stage during the third round
- Capcom vs. SNK - appears in Vice vs Rugal intro sequences
- SNK Gals' Fighters - with Miss X
- SNK Heroines: Tag Team Frenzy - in Miss X's ending
- ↑ http://game.snk-corp.co.jp/official/kof-xiii/arcade/character/
- ↑ Official character profile from KOF anniversary website
- ↑ Official character profile from KOF anniversary website
- ↑ http://kotaku.com/5285750/the-king-of-fighters-xii-for-novices