My Sly Bestie

Mana's only friend during high school was a girl by the name of Himeno Takatou. They reunite as adults and Himeno has become even more stunning than before. While catching up, Himeno asks about Mana's love life and learns all about the man Mana is interested in. Then after hearing that Himeno had just gone through a divorce, Mana invites her to a barbecue with her colleagues to cheer her up. However, the Himeno who shows up dresses and acts like a totally different person! Little by little... another side of Himeno begins to surface.

(Source: MangaPlaza)

Note: Includes two extra chapters.