My Brother the Shut-In Vol. 3 (Kodansha, 2018)

When you care about someone more than yourself, they call it ""love."" Shino Tadokoro has an older brother Tamotsu who used to be a shut-in. Shino is rapidly closing the distance between herself and her first boyfriend, Natsui. On the other hand, she is beside herself with worry as Tamotsu's heart is held captive by the little coquette Inaba-san. But as she watches over her brother's pure and awkward romance, a change occurs in Shino's heart?! As both love stories pick up speed, the siblings' relationship changes, too!!