The "reunion" single will be released on April 17, 2013. Their new single will have three versions: Standard Version [CD only], Limited Edition [CD + DVD], and OreImo Version [CD + Anime Illustration Digipak].The OreImo Version will have one track different than the other two, most likely addition of a TV mix version. There is no information about the other songs that will included in the "reunion" single.

UPDATE: ClariS new artist illustration has been announced! The illustration is Hiro Kanzaki (かんざきひろ). Hiro Kanazaki is the original illustrator for the OreImo novel, the character designer for OreImo anime under the name Hiroyuki Oda (織田 広之), and the first illustrator for ClariS. The new image for ClariS is posted below. 

Be sure to keep an eye on further news about ClariS and their new single! Also, feel free to check out t-ono’s articles and first English interview with ClariS under the “Related items” below.