ぜんぶ君のせいだ。(Zenbu Kimi no Sei da.) has announce a new, untitled, single to be released on April 26, 2017. According to their discography page it will contain three tracks. Other than that we really have no other information.
They did include this photo with the post.
＊画像はイメージです。 (this roughly translates as: this is just an image)
Official Website: http://kiminosei.com/