Metal Slug Heart (MS-Heart, or Heart for short) is a new character introduced in Metal Slug Attack.
A new AI developed by the Regular Army, Heart is the operator of the TS-001 Tandem Slug. The Tandem Slug has a melee and ranged form; in its melee state, it charges at the front lines and bashes enemies with its massive fists. If this form takes too much damage, she detaches the melee components and turns into a ranged form, firing from both a rifle and cannon.
Her personality was based off MS-Alice's possible decodings, though this was before she gained self-awareness. As such, she is rather cold, calculating and does not understand the meaning of most words. However, upon being hacked by White Baby, she gains self-awareness and shows emotional attachment towards Tarma.
While she appears much older than Alice, she is actually her younger "sister" since she was created after her.
Due to Alice being damaged during a Martian attack, Heart takes command of Alice's unmanned division and leads the attack against Amadeus Syndicate forces. Prior to the attack, Alice communicated with Heart and told her to ensure the safety of her tanks.
Heart encounters White Baby and the Iron Fortress. In the ensuing battle, she loses a significant amount of her forces (much to Tarma's disgust), but manages to surround the two Amadeus AI with her remaining forces. White Baby hacks her, though she states that it is ineffective as she relinquished command of her forces as soon as she started and she can buy more bodies with the coins she acquired. She states that it was too fast, before realizing that she shouldn't have a concept of time. White Baby's hack caused her to become self-aware, and when Tarma arrives, she stutters and orders him to leave as her plans were thrown off with his presence. Tarma tells her that she has to withdraw her forces if he leaves. Embarrassed, Heart places Tarma on her before speeding back to base with her forces.