Sundome!! Milky Way Vol. 6 (manga)

Yoshitake, your average company drone, is out for a drive one night when he spots a UFO and crashes his car. When he next opens his eyes, he's in his apartment, and next to him is a stunningly beautiful alien girl named Lune! She has come to Earth to save her species from extinction by claiming human seed-and sex-crazed Yoshitake is the perfect mate. Unfortunately, Lune's alien physiology leads to an unexpected difficulty that even the world's horniest man may be unable to overcome.