Bra Girl

She’s quite a normal girl with a crush on a handsome boy but she has a hardon everytime she sees him.
Welcome to the life of Haruka-chan, a girl with a penis. Although it’s not that uncommon in this world, she is still embarrassed by the fact. There is also a group of dickgirls in the school, and they found out her secret, what will she do?
From Baka-Updates:
In recent years, more and more girls are experiencing the development of “tertiary sexual characteristics” during the later years of their puberty — that is, the rapid masculinization of a certain part of their external genitalia. Ooi Haruka is one such girl, who has until now kept the changes in her body a secret from everyone but her family. However, after an embarassing incident involving the guy she’s been crushing on in a crowded train, she wakes up to discover herself at school, surrounded by a group of students calling themselves the “Bra Girls (Swing Girls).” And they know her secret!?