This Chubby Girl Can't Stop Acting Like a Little Devil is a Manga/Manhwa/Manhua in english language, Comedy series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

"'Issues with love'? What was with thaaaat… I don't have any right to say that…" Tsukiyono Mayoi, 16: A second year at Oujibaru High School, and a part of the school's Library Committee. Whenever she's in front of the kohai she likes, Amagi Haru, she acts like a clingy 'little devil' character. It's not something she does by choice, but rather, by necessity. Here unappealing figure and low confidence makes her insecure, and forces her to put on an act in order to talk with the guy she likes. And so begins the story of a chubby girl that just can't seem to stop acting like a little devil character.