Pinky swear

Title seems odd but there is FL who teach pinky swear in different way to a kid or ML or both 

I don't remember whole details but it's like this 

Write , scan (when they rub hands with each other like scanning), stamp (last step of pinky swear where they join the thumbs).

Drama is from China,Taiwan ,korea. Mostly it's from chinese drama. Please help to find this drama