Tomo-chan is a Girl! Vol. 6 by Fumita Yanagida
High school tomboy Aizawa Tomo finally manages to tell her childhood friend Jun that she's got a crush on him. Unfortunately, her confession goes right over his head - he didn't even realise she was a girl until middle school, and even now, Jun still thinks of her as a bro! How can Tomo-chan possibly convince Jun otherwise to win his heart?