I don't know the name, but I remember the plot. It's about the youngest daughter of four girls. Her father is a writer and her mother was dressed in a generals uniform. She goes to school the next day and sees the students making a path for a group of boys, the leader was whistling and tossing acorns. She sees him again sitting in the rain next to his crashed motorcycle and gives him her umbrella. She meets a little boy while grocery shopping buying carrots for his bet bunny, Jenny and her babies and we later find out that the little boy is the younger brother of the leader.
I think the manga is shoujo.