Zuo Ri Ru Si

When Xi Zhonghe got dumped five years ago, Gu Tang was there to witness it and helped him to get over the heartbreak. But when Xi Zhonghe got into a car accident and lost his memory of the rejection, he didn't remember Gu Tang anymore and he wanted to get back together with his ex instead. Gu Tang: "......."
(Source: Bilibili, translated)
Note: Includes prologue and eight extra chapters.