Futsutsuka Mono no Ani Desu gaMy Brother the Shut-In; ふつつか者の兄ですが

Every family has its share of problems, be they big or small. Shino Tadokoro has the perfect high school life, full of romance and friendship. Her biggest problem is her shut-in brother Tamotsu. She stubbornly keeps his existence a secret, telling even her closest friends that she is an only child. Completely oblivious to Shino's concerns, Tamotsu suddenly declares that he is giving up the shut-in lifestyle. Is there still time? The curtain rises on a tale of family reconstruction! [Kodansha]