18+ Kamiyama-san no Kamibukuro no Naka ni wa

On Namito Kominato's first day of high school, he fantasizes about making friends and walking home with a girl. Luckily, he's seated behind a gorgeous girl in class! She's tall, strong...constantly dripping with sweat...and...she wears a paper bag over her head?!

Meet Samidare Kamiyama, a kind but shy student with severe social anxiety. Though Kamiyama couldn't talk her way out of a wet paper bag (literally—it's hard to breathe under there), Namito gets her to open up. The pair become fast friends, and soon enough, the outgoing, uniform-obsessed class representative is joining in. Together, they decide to found the "Conversation Club" to help Kamiyama participate in high school life. The club needs four members to become official, and there just so happens to be the perfect addition: a student who can only talk to a cardboard cutout of a magical girl!

When given a welcoming space to be themselves, even social outcasts can flourish. Let the first meeting of the Conversation Club commence!

(Source: J-Novel Club)