Asriel will be participating in C77, which is something of a surprise since in recent years they only released new doujin material at M3. In any case, their latest maxi single is called Devils Lullaby, and it will have 3 tracks. Samples tracks are available on the website.
little white snow's latest is an original vocal album called Snow White. A preview edition of one of the songs to be included in the album was released at M3-24.
MiddleIsland will be releasing an original vocal album titled Frizzell Weisen. It will feature Nakajima Misaki and five female vocalists, including Murasaki, 睦鬼 (Mutsuki), 坂本千明 (Sakamoto Chiaki), 蒼咲雫 (Aosaki Shizuku), and Yuka.
P.S. What's with the sexy cover art?
Seifuu Meigetsu will be releasing HAMELN Limited ver, which will contain two songs from HAMELN (released at M3-24), one new song, three instrumental pieces, and two voice drama tracks. Hatsuki Yura will not only be responsible for the vocal, she will lend her voice in the drama tracks.