From Be Beautiful:

Ryuya was only trying to finish his University courses so he could get started with his life. Everything was going along fine, until the wealthy and gorgeous Orito nominated Ryuya as the vice president of the prestigious Honors Society. Most people would jump at this opportunity, but Ryuya isn't interested, and Orito isn't backing down! It seems that campus politics and advanced studies aren't the only things on Orito's mind, and Ryuya is shocked to discover that his newfound suitor always gets what he wants...

Otona to Kodomo no Kyoukaisen (roughly means A Man-Child's Boundary Line)

From Peccatore Sanctuary:

Tohru is confused and in deep trouble. After the 'thing' with Takafumi - a senior high student, Tohru can't get him out of his head. Tohru swore that he will wait until Takumi is legally an adult he will not do 'H things' (perverted things) with him. However, both are finding it hard to keep their urges under control... this is when the line between boy and man becomes conveniently blurred...

Upon entering Takamanohara Academy Waka meets Moriya, a strange boy who seems to know him, though the feeling isn't mutual. Despite not knowing who Moriya is, Waka feels a strange pull to him. When he gets an invitation to the mysterious "Gentleman's Meeting" he can't help but be fascinated and a little worried all in one. Upon entering the Shrine's archways, Waka's future becomes increasingly unclear.

Can't Handle Brats?!
Tohru is a policeman who works at a police box when he confronts a teenager for shoplifting who turns out to be his one and only younger cousin, Takafumi! As children, Takafumi was constantly mean to Tohru, but now...

From Kawaii Corner:

On the first day of high school, because of a conditioned response, Kunie Hokuto injured Yachigusa Shissa, the disciplinary committee chairman feared by students throughout the school. He listens to Shissa's remarks and agrees to be appointed to stay with him as his servant, in compensation for the injury. In addition, without knowing why, he is designated as a first-year representative to the disciplinary committee, but the disciplinary committee vice chairman, Shissa's younger brother, Zento, declares, "I do not approve"...!?

From Fantasy Shrine:
Taking care of his homeroom teacher, Wakasa-sensei, the kindhearted Kakeru is the only person who knows the outwardly charismatic teacher is in truth, a bully! Whenever they are alone, Kakeru tries unsuccessfully to evade Wakasa’s advancements. However, Kakeru couldn’t help noticing Wakasa’s tenderness at unexpected moments. And then, at the start of the 3rd year in high school, a new teacher from Wakasa’s past and a new student arrive…

• Unexpected Disaster
When the cat he's not supposed to have gets into his next door neighbor's house and makes a mess of some valuable paintings, a young scuba instructor finds himself blackmailed into nude modeling by the perverted artist.

Haruma is a good looking son from a rich family, but he wants to live his life on his own without any help from his family's money. However, his mother hires a cheeky bodyguard to watch him 24/7 and things get out of control. His bodyguard Kurehashi, Shouyou is smart, good looking and knows several things that Haruma doesn't. Kurehashi vows to protect Haruma and to teach him what it takes to live in the real world, even if that means stealing Haruma's first kiss!

Description by LuffyNoTomo