Millefie is a new character introduced in Metal Slug Attack.
Millefie is a fairly young and shy woman who has served in the Rebel Army for a long period of time, during the time the Professor was the head of research and development. The Professor allowed Millefie to do whatever she wanted, having electronically wired her money whenever she needed it. Millefie eventually designed the Iwa Oh, a Tani Oh-like variant that utilizes quantum energy inspired from the Mars People.
Due to avoiding the company of others, Millefie also customized the inside of the Iwa Oh to serve as her living quarters. Spending her time alone, she was apparently forgotten by the Rebel Army, with no one even attempting to look for her, although she still remained loyal. After being brought back into service, Millefie fortified her Iwa Oh with additional armor.
Although she is unwilling to give up and is a hard worker, she prefers to work on her own pace and dislikes it when others pressure her to work faster. She also has a younger sister, Sylfie, who also works with the Rebel Army.
First appearing in "United Front the 19th", Millefie and the Iwa Oh are discovered by Emma. Emma somehow recognizes Millefie, though she is initially unable to get her out until she mentions the Professor deserted the Rebel Army. This prompts Millefie to get out, and she learns from Emma that Navy is their current chief. Millefie is horrified after realizing that with the Professor gone, she can no longer get money to survive as she had depended on him to electronically wire her, to which Emma points out that time is money and she needs to participate in the United Front, much to her surprise.
After the United Front has ended, Emma orders Millefie to go to the United Shop, but she can't go there without the proper clothes for shopping. Emma eventually persuades Millefie to go there before it closes insisting that the Iwa-Oh is not a place to stay, but the sunlight and her lack of integration with society made her run back into her tank in fear. She asks Emma to help deliver the items to her, but Emma applies a service fee in which she would have to return to the Rebel Army and work again, much to her dismay.
- The name "Iwa Oh" (巌王) translates to 'Cave King'.