Double Knight

is a japanese 4-koma manga series written by Tamaoka Kagari. It began serialisation in the  issue of Manga Time Kirara.

The series was released under 2 volumes from September 2008 to February 2010.

Synopsis
Natsuno Inama just recently moved to a new condo with her dad and meets her new next door neighbors, Shiroyanagi Yukikage and her younger sister Kanon. They immediately hit it off when they learn they attend the same school. With her new rival(?) Kazain Ibuki in her life, Inama’s life is full of surprises and fun.

(Source: MU)