LOVELY DAYS is the Leaflet of Volume 6 of the Citrus manga. It was released on December 17th, 2016. It consists of the stories Momoiro Shimai 1 (ももいろ姉妹①?) and Momoiro Shimai 2 (ももいろ姉妹②?). As the titles imply, both stories center around the manga Momoiro Shimai.
Momoiro Shimai 1
After Nina finishes reading Momoiro Shimai, she becomes influenced into thinking that she could be lovers with her twin sister, Sara. When Nina makes this declaration, it initially scares her sister off.
Momoiro Shimai 2
As Yuzu finishes reading the latest Momoiro Shimai, when she gets home she noticed Mei is fast asleep, As Yuzu is watching Mei as she sleeps, Mei hugs Yuzu to Yuzu's surprise, but it turns out Mei confused Yuzu with Kumagorō. This causes Yuzu to get mad at Mei, much to Mei's confusion.