Im not good at words-ing but
Koharu Sakurada and Aki Tamaki
Sakurada means "Cherry Blossom field"
Aki roughly translates to "Autumn"
Cherry Blossoms are not only associated with love, but their short lived blooms also signify the fleeting nature of life.
Autumn is the time of the year where trees shed their leaves, and is associated with grief in some cultures. But at the same time, it signifies new beginnings.
Koharu died young. Too young. Unlike Aki who had loved her since she was only nine years old, Koharu never had a chance to experience falling in love. And i think Aki feels guilty for that. For not confessing sooner, for not confessing later, for confessing at that place, at that time. Maybe then, she would still be alive, she would still have had a chance at experiencing love. And maybe she feels guilty for surviving the accident, for not being the one who died instead, for not being able to save her.
And moving on doesn't mean she didn't love Koharu any less, it didn't mean she didn't love her anymore. In fact, its the opposite.
Even years after her death, Aki still loved her.
She loved her for six years, and continued loving her for five more.
Aki loved her, and though that love and grief may not fade away anytime soon, she has to move on. For herself, and for Koharu.
Those cherry blossoms will bloom again one day, and though those flowers aren't the same as the ones from before, they are just as wonderful.