The Sisters and the North Star

After their parents remarry, classmates Hikari and Mizuki suddenly become stepsisters. Hikari is calculating and shrewd, deliberately positioning herself within the popular crowd at school. In contrast, Mizuki is awkward and painfully honest—so much so that she becomes the target of bullying. With completely different personalities and social standings, the two clash at first. Yet as they spend time together, feelings they could never voice to anyone else begin to surface, and little by little, they find themselves drawn to each other.

(Source: MANGA MILLION)

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

Note: Includes 8 extra chapters.