Thank Yaoi For Existing

probably not the best description in the title but I'm searching for the name of a manga I read a couple of months ago, about two school boys who play the game walking home from school where you walk along the line of a road marking and if you step off the line accidently you "die", and they walk past each other on the line every day and fall in love, and in later chapters it goes through their entire lives together.

It was SO CUTE and tear-jerk-y, I really really want to read it again. Anyone know what it was called? ;A;