Tensei-saki ga Shoujo Manga no Shirobuta Reijou datta

Synopsis

I recalled memories of my past life after Grandfather told me my engagement was annulled. At the same time, I realized this world was the same world as in my favorite shoujo manga. The villainess who exhausted every method possible to bully the heroine... I reincarnated as that villainess' chubby follower. I shook upon remembering the future lined up for her. When the villainess' evil deeds came to light, she pinned all her crimes on Britney. I was a character that gets executed. To reliably avoid this, I must not become the villainess' follower. As this villainess only keeps those who are exceptionally uglier than her by her side, I may be able to do something if I slim up. For now, let's go on a diet! (Source: Shousetsuka ni Narou, translated)