SECRET DIET MAGIC: FROM CHUBBY TO SLIM... AND MATING LIKE RABBITS?!

Sota's childhood friend, Rin, is known around school as the "Sad Cow Girl", but then one day suddenly transforms into a slim and slender smoke show with big boobs and a skinny waist. The one twist was that in order to achieve this new body, she had to pay the "price" of always being horny. With such, their normal relationship of childhood friends was forever changed. The old days of playing over at Sota's house or hanging out at school, were all destroyed by Rin's moans and newfound desires. While deep down, Sota wants things to return to the way they were, he can't get over how good it feels to bang his childhood friend! (Source: Coolmic) — Description from AniList community (anilist.co).