Kyun to Sasende Miyabe-kun

Ruka is 14 years old. Today, she's going to marry the man of her dreams! She's going to live with of Miyabi-kun, who she promised to marry 8 years ago. But when she meets him again, he's become a really cool guy... Is Ruka the only one who remembers their marriage promise? But he helps her out when she's in trouble, and even says things like "It's fun being with you, Ruka"!

(Source: Shogakukan, translated)

Note: Includes two extra chapters.