Momoka Sakurai, more known as ' Menhera-chan, the wristcut warrior' is the main character of the Men. Google is your friend
https://menhera-chan.tumblr.com/about dis? (Further reading: https://fymenhera.tumblr.com/info) Or if you mean the dark haired gal, that's art by this person: https://twitter.com/pomujoynet1?lang=en
... https://store.line.me/stickershop/product/1914987/en https://menhera-chan.tumblr.com/about ...So which one is the Menhera-chan the OP talking about? Or they are both the same person?....Seriously, finding this new Line sticker about this Menhera-chan, then this manga Menhera-chan....I don't even know....