Futari no Polaris

Two people who have never talked before suddenly become sisters...? A sparkling friendship story! Hikari, a girl who thinks keeping up with everyone is annoying. Mitsuki, a girl who is bullied by her classmates. One day, Hikari's mother and Mistuki's father decided to get married!? Even if they don't get along, they decide to become sisters...?

(Source: Shueisha, translated)

Included one-shot:
Volume 3: Nijika ni Naritai
Volume 5: Kyou kara Ii Ko Yametemita