Considering that Tomozo Kaoru drew it, the characters depicted probably are Furude Rika and Sonozaki Mion from Hinamizawa Teiryuujo, yet another Higurashi manga, this one based on the prototype idea that preceded the original game where Rika was a year older than Mion.

I wonder if this Rika is bigger than Rena or not but Ni-Pai