Hanami = Hana + mi. Hana means flower and mi mians viewing. We often go out to a park with basket of lunch(dinner) and drink(alcohol) to see sakura blossoms. Like this. 
Sakura represents the feeling of vanity, fragility or short life because sakura blossoms don’t last for only a week. They soon fall especially when it rains. And April is the season of parting, graduation, and mixture feeling of anxiety and hope for starting a new life. (In our country, school and comapany term starts from April.) We overlap sakura on such feelings. Therefore, although there are hundreds of songs of which title includes sakura, most of them are songs of parting.