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 year, but Adachi doesn't seem too pleased with the fact that Shimamura is having no trouble fitting right in with their new classmates. Acquaintances, friends, best friends--those are all well and good, but how do you take that final step? Maybe having a sleepover and sharing a bed together...?