Kanojo ni Uwaki Sareteita Ore ga, Koakuma na Kouhai ni Natsukareteimasu is a Manga/Manhwa/Manhua in english language, ROMANCE series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Hasegawa Yūta found himself single after breaking up last month. After an everyday conversation with his female friend, Mino Ayaka, Yūta met a beautiful girl clad in a Santa suit—In a lane full of couples no less! Her name was Shinohara Mayu. Will this encounter with Shinohara turn out to be the Christmas present for Yūta ?