I haven’t read this manga, but it has won awards and I have heard good things about it. The synopsis from Kodansha:

Hotaru is a 16-year-old high school first-year who has always been ambivalent about love, preferring instead to have a lively life with her family and friends. So when she sees her schoolmate, Hananoi-kun, sitting in the snow after a messy, public breakup, she thinks nothing of offering to share her umbrella. But when he asks her out in the middle of her classroom the next day, she can’t help but feel that her life is about to change in a big way

They also announced casting for the lead roles:

• Kana Hanazawa as Hotaru Hinase
• Chiaki Kobayashi as Noi Hana