The umbrella, when it rains - Kakashi
The popcorn at the cinema - Sakura, else Kakashi eats it all before the trailers begin.
The baby, when it cries - SAKURA, Kakashi makes sure he is nowhere to be found.
The ice cream cone, when they share - Sakura. Sometimes, when she's in a silly mood, she'll boop his nose with it and laugh.
The remote, when they sit down to watch a movie - Neither. When they're watching a movie, they hold each other.
The basket, when they go shopping - Sakura makes Kakashi do it while she loads up the basket with groceries.
The door, on dates - Kakashi. He's old fashioned like that. On the other hand, Sakura tends to rush in front of him or string him along, so she'll open her own doors, thank you very much.
The other’s hand, most often - Sakura, she initiates most.
Their breath, upon seeing the other on their wedding day - Neither, Kakashi just smiles upon seeing her, and she answers with her own because for the day's occasion, he's agreed not to wear a mask, so everyone can see how happy he is to see her come down the aisle.
The camera, when they take pictures together - Sakura. Kakashi isn't very inclined to take pictures at all, but Sakura wants to 'collect memories'.