memories: When Chihiro gets e-mails from her sister about Kei's own life, Kei writes about events that happen during the summer, when it's winter where Chihiro's side is. Then comes The Reveal where you find that the Chihiro's side is living on a second Otowa. In Australia. Thus, the season are reversed.
In melodies, think back over the course of the entire game, and how each couple slowly got shoved towards figuring things out. Yuuko always brutally exposed the problems everyone had to force them to face up to things, but who gave them the crucial last-second encouragement? Mizuki. Considering their backstory, this only makes sense.
What does "Ef" stand for? Apparently, there are plenty of songs that has "Ef" as initial, including in the Visual Novel. Eternal Feather. Emotional Flutter. Ever Forever. Euphoric Field. Ebullient Future. And Now You Know.
The anime scene where Renji and Chihiro finish their date with Their First Time is very cute... And then you realize that, considering Chihiro's condition, it could have ended up with Renji taking advantage of Chihiro's amnesia kicking every 13 hours to trick her into believing that it didn't happen, and thus they should have "Their First Time" again. And again.. Thank the Gods that Renji is the kind of personwho would NOT do it.