What makes the Momoko-verse so interesting is the incredible adaptation work Momoko did. Both her arcs feature many alternate versions of iconic Marvel heroes and villains, revamped to fit a Japanese, anime-like aesthetic. While some of these reinterpretations are obvious, others take a bit of analysis to make sense. Only a keen-eyed Marvel fan will go through this story without having to search the internet for clues.
The Momoko-verse strives to create a new, fresh, alternate world for the Marvel multiverse, but this task needs a proper axis. Peach Momoko chose Mariko Yashida, and the whole Momoko-verse revolves around her story. While Demon Days introduces her as a character, delving into her past, Demon Wars puts her in the middle of a conflict she barely knows.
As a character, Mariko changes plenty from her canon version. For starters, she's a human/oni hybrid. Instead of coming from a villainous family, she was raised by an adoptive grandmother, and she never dates or marries Wolverine. Her design and origin remind fans of her time as the Scarlet Samurai, but it's still too soon to see if Momoko will keep this moniker for her.