Hello Goodbye(2007)

Hello Goodbye

Mutsuki is heartbroken after being suddenly dumped by her beloved boyfriend, Nakatani. While she's devastated, she wakes up to find herself in the bed of the notorious playboy, Noda! A love triangle begins from this heartbreak—what will happen to Mutsuki's true love story? Could heartbreak be the beginning of happiness...? The ultimate guide for overcoming heartbreak!

(Source: Kodansha, translated)