7th period is a secret manga

7th Period is a Secret summary:

From Serenus Dreamers: Shun is a girl who used to be shy and gloomy. Wanting to change, she transforms herself into a bright girl when her family transfers into a new place. Hoping to fit in, she laughs and smile at everything agreeing with everyone. She starts to fear that her young teacher is seeing right through her. Is she just imagining, or is it true---? Also contains two one-shots: Your Kotonoha (Your Words) Yuki's childhood friend, Rio, suddenly moves back. Two years ago, she confessed to Rio through a letter; but Rio read it out loud to everyone and made fun of her. Rio still has the letter and threatens to recite it unless Yuki does what he says. Puberty Baby To Eri, Kaoru is like a troublesome little brother or a cute puppy. She's been taking care of him for fifteen years since they live in the same apartment. She thought he had no interest in girls but that changes when she catches him with a group of girls and flirting!