Onegai☆Teacher, Asobi ni Iku yo! Recommendations
Also sci-fi, comedy, romance, a female alien and the male character look similar aswell.
Very similar settings of an alien coming to Earth and eventually falling in love with the male MC.
The male MC's are VERY similar, they even look the same! Both grow mentally stronger over the course of the series but they're both still a bit of a push-over.
Onegai Teacher focuses on hiding the existence of aliens while Cat Planet Cuties flaunts showing off the aliens to the world.