Adachi and Shimamura, Vol. 4 (manga)

Adachi and Shimamura are now in their second year of high school. Luckily, they're in the same class this semester, but when Adachi sees Shimamura making friends with their new classmates so quickly, she starts to panic. Feeling left out, she begins distancing herself from Shimamura, who can't help but notice that Adachi's been on her mind a whole lot these days...