Aero

Aero is an alien of uknown origin. He never tells of his planet once he is actually allies since in his culture betrayal means that you are no longer a member of their socity. He still has family there so he honors this rule. He was a very skilled assassin, the best on his planet. The Elders of his planet sent him to kill the teenage Lillia. Warning him that all attacks had been foiled thus far by the Z Fighters.
Aero decides that he will go with a different stratagy. He decides to meet and befriend the trusting Lillia. He is surprised how easily she trusts him and how quickly she becomes his friend. But he keeps working on building up the trust with her and her family and friends.
After 6 months he decided it was time to kill her, so him and Lillia are haning out talking when she turns her back. Aero takes out his blessed knife to kill her. But Lillia turns around. Much to Aero's surprise she is smiling. What surprises him more, she says that she loved spending time with him so much, that eventhough she knew he was only getting close to her to kill her, she couldn't help but want to spend time with him.
In his shock Aero drops the knife, cutting open his hand. In a panic Lillia leaves, Aero thinks he has just lost his chance, until Lillia returns with a first aid kit, and bandages up his hand.
Aero never experiancing this kind of reaction flees. He knows he can't return home until he kills her, so he starts fallowing her around. Only to see her get attacked more. He starts using his abilities to take down her would be assassins. He first reasons it as he has to be the one to kill her. But he starts to realize that it is a totally different reason to why he has been saving her, he was in love with her. 
Surprised by the revolation that he loves her, he decides he has to tell her how he feels. So he finally emerges from the shadows after 6 months of hiding.
He tells Lillia how he feels about her and again her reaction surprises him, he had prepaired himself for rejection, when Lillia kisses him. She says she knew he was in love with her and was wondering when he would tell her. Then she tells him that she loves him too, then much to Aero's surprise that he is now her boyfriend.
Her family doesn't take to him to well this time though. No one does. It takes time, but they see how Lillia feels about him and eventually Aero joins the ranks of the Z Fighters. Though it takes a lot of effort from Trunks to teach him not to kill people who piss him off.
===Personality:===
Arrogant, Serious, Always ready to Kill, Short Tempered. but around Lillia: Sweet, Kind, Shy.
===Trivia:===
-He never reveals what species he is.
-He mentions a little sister, a sister who later makes an appearance. The only one in his family who didn't cut all ties with him when he decided to be with Lillia.