Every time I have heard Memorial, it's always been in reference to someone's death.
As a side note, a Memorial Service is like a funeral... the only difference is you don't have the casket.
So it's saying she's mourning someone's death (by all indications, her father's death). And this song is the Memorial Address or the message given in honor of that person.
I think so many of Ayu's titles are very skillfully named... Even if the title isn't said in the song, she's good at choosing titles that really sum up the essence.
