If you're looking for manga similar to Tenchi Muyo! GXP, you might like these titles.
Sasukiba Sorata is a genius swordsman in an age where magic is all he has to face as a swordsman without magic. The story begins when he accepted for his talent in Enbu Academy of magic only for women, he meets Felicia which it is the number one magician and leader of "Seven-Star Knight", the meeting was intended to cause drastic changes the fate of the world. When the strongest swordsman must undergo seven sorcerers - A new legendary history!
Shun Yanahara is a pretty normal first-year high school boy. His grades are not terrific, he's not very popular with girls, and he plays soccer with his school's club. He's often felt like someone was watching him, and, strangely enough, he's right. On a far away Earth-like planet known as O-pa, there is a civilization made entirely of women. One of them, a scientist named Lib Myura, has fallen in love with Shun. She and her two colleagues have created an illegal male human robot, called a synchroid, which they intend to fill with Shun's consciousness. However, things never go exactly as planned...
Hiroki's passed his high-school entrance exams, and now he's looking forward to a peaceful, lazy spring vacation before the entrance ceremony. All of that is ruined on the morning he's woken up by Hinata, a stranger who claims to be his childhood friend. The truth is, Hinata is a "tsundere childhood friend" android made for him by his mad scientist neighbors in celebration for him passing his exam! With all the complications his new "childhood friend" is going to cause in his life, what will happen to the peaceful vacation Hiroki had hoped for?
Mina, a Lieutenant of the Space-Time Vanguard Unit arrives from the distant future to interrupt Ichikawa's peaceful life with some upsetting news of how the world would end-up if he continues to pursue his affection about his little sister. The sound of the grim news doesn't seem though to deter Ichikawa resulting in Mina having to take any and every possible action to convince and if necessary seduce him!
Three quarters of the world is the world of the dead. The world has been invaded by phantoms. One day, a boy named Nagi finds in the mountains of scrap wood a mechanical teenage maid girl. He immediately takes her home to repair her. The first things that Elise, this mysterious mechanical maid, says is, "Good morning, Nagi." Who is this mysterious silver haired girl? The fate of the world rests in their hands.
Invaders from another world are attacking the Earth, and humanity's only hope lies in special armors called Hybrid Heart Gears, or HHGs. Hida Kizuna might seem unexceptional, but he has a skill that can turn the tide of battle--by getting female HHG users hot and bothered, he can replenish their energy!
Hitoshi Kobe is pretty dumb, not good at sports, and extremely unpopular. The only thing he IS good at really is creating artificial intelligence programs on his computer. His greatest work is number 30, one which very accurately simulates talking to an actual girl. One dark and stormy night, a freak lightning strike causes number Thirty to emerge from his computer screen as a real girl, and sends Hitoshi's life on a turn for the crazy.