I try to remember the manga name but only remember one scene which is the female lead try to serve the two guys which come as customers the cups of tea. The situation is that the school is having the festival the class is doing the cafe for the theme. One of the guys who come as customer is left handed and the female lead observe and know that he is and change the direction of the cup handle to be more convenient for him. And he is surprise to see that how she know he is left handed.

Not 100% sure but it might be Honto no Kanojo.