Oh hey, haven't written my thoughts here yet...might as well do it now!
Avalon - I like the incorporation of pianos, and the overall lighter atmosphere (but has that "MEJI' punch" too, of course). MiA once again provides some cool melodies/solos on his guitar, and Tsuzuku's voice is nice too. Essentially no different than their usual fare but good enough. Catchy stuff!
Kokyuu - Again, the piano, a nice touch! Starts off rather interestingly, and gradually blooms into pretty okay-ish pop. The chorus reminds me a bit of Kore wo izon to yobu nara, maybe not a coincidence (since Tsuzuku references those lyrics towards the end). Not bad, but not too memorable.
D.E.INCUBUS - This one smells like The GazettE at parts, heh (the main riff and chorus). I can listen to it but, all in all, totally forgettable.
Overall this was an okay-ish single, nothing too extraordinary but not unlistenable either. I like how they usually maintain an "average/good" quality throughout their releases, although I'd much rather they began taking more time to polish their songs into being more well-thought-out because the lack of variety is beginning to show. I'd give this single a 6.5/10 - not bad but step up your game a bit more, guys!