Mashu is the Asset that aids Yoga Kimimaro during his struggle inside the Financial District. She really likes noodles and is curious about kissing.
Mashu didn't exist in her current form until Yoga agreed to enter the Financial District. She then accompanied him at all times and dutifully aided him during Deals inside the District. She surprised spectating Entrepreneurs, as well as herself, with her display of power in Yoga's first Deal. Her powers are all flame-based and scale in strength to match Yoga's elected level of 'flation' for each attack.
Mashu was at first indifferent and, at times, stubborn in her relation to Yoga, though she gradually developed a fondness and love for him. It's difficult to tell if Mashu grew intrinsically stronger as a combatant during the narrative of the first season of C.
C - Control
Mashu is 'born' with little knowledge of herself or her relationship to Yoga, only seeming knowledgeable about how to use her powers in fights, or Deals. She is even unaware of how she represents his future. She views Yoga as too sentimental or absent minded because he lacks the drive to simply win a deal.
As the series progresses and Yoga considers the consequences of each Deal and makes his decision of who to support within the District, she acknowledges his good nature and realizes she has an affection for him.
Though the two may disagree on the nature of their relationship, they decisively pursue their goal of eliminating the Financial District and taking back the lost future of Japan and its people.
After the final battle concludes and the future is re-materializing, Mashu finally gets her wish to kiss Yoga the same way she saw a romantic couple kiss on TV. She then disappears because Yoga's future is no longer collateral to the Midas Bank.