From MangaHelpers:
Hori may seem like a normal teenage girl, but she's a completely different person after school. In her workaholic parents' absence, Hori has been like a parent for her little brother since she was young herself. Between taking care of her brother, feeding them both, and housework, she doesn't have much time for a usual teenage social life. One day, she meets someone else who does not present his true self at school: a quiet, glasses-wearing boy called Miyamura. She'd assumed he was bookish, and possibly an otaku, but Hori couldn't have been more wrong. Outside of school, Miyamura is a friendly guy with many piercings, and he's not very good at academics. Now the two of them have someone with whom they can share both halves of their lives! [tethysdust]
From Shoujo Crusade:
Hori is your average teenage girl... she has a side she wants no one else to ever find about. Then there's her classmate Miyamura, your generic glasses-wearing boy in school and a totally different person outside. When the two meet unexpectedly, they discover each others' secrets and develop an unexpected friendship.
Horimiya