From Gensokyo:

Based on the hit manga by Katsu Aki, "Futari Ecchi for Ladies" takes the story to a new level.
The newlywed story continues, but this time around, the perspective is from Yura, our FE heroine. This tale adds new twists and problems that women encounter.

Fuuta is an average-looking salaryman who's never had luck with women. However, all that changes when he meets a strange girl through a dating agency. She's nice, but has an odd habit of always wearing masks on their dates. One day, Fuuta sees his mask-wearing girlfriend being attacked by (what he thinks are) thieves. Fuuta saves her from them, and full of happiness and gratitude, the girl confesses and proposes to him. The night they get married, she finally takes off her mask and reveals her identity: She's the super-idol singer Kirari who Fuuta admires! Thus starts their life as a married couple.

From Tokyopop:

Zerodaimu Kyupura Pa Azalraku Vairu Rua Darogu (a.k.a. Zero) once stopped the evil demon lord with his incredible psychic ability, and in the process saved the world from destruction and earned the honorable and highly imaginative title 'The Man Who Stopped the Evil Lord.'

Now, he has accepted a position as a teacher at Psychic Academy, a school for gifted psychokinetic youngsters who have demonstrated incredible raw powers and want to learn how to hone their abilities. Among the student body is young Ai Shiomi, Zero's little brother, a somewhat meek boy who, despite parental prodding and his fraternal reputation, feels that his limited skills hardly justify his presence at the prestigious academy.

However, everyone else is convinced that he, like his celebrated brother, is destined for greatness. A lot of pressure for a boy just entering adolescence!

Kyoubei Kurokawa, a university student, is aimless in life and has run away from his home to live alone but has nowhere to sleep. One day, his life is saved by Asumi Nanjou, a mysterious girl from the same university who takes him to her apartment to treat his injuries. After hearing of his situation, Nanjou decides to let him live in her home but under one condition: he will be an invisible man. He later discovers why: she will completely ignore his existence. Meet Kurokawa and discover the advantages (and disadvantages) of being an invisible man and unraveling the mysteries behind Asumi Nanjou.

An excellent and very educational series. About a newlywed couple who are virgins and their comedic ups and downs in learning how to have sex. Not really a hentai, though there are scenes which can be called hentai. Tastfully rendered taboo themes. A funny "how to" guide for sex illiterate and experts.