Fantastic Children, Boku no Chikyuu wo Mamotte Recommendations
The stories of Fantastic Children and Please Save My Earth involve reincarnations attempting to make amends for their past sins. And love is an important aspect of both.
Fantastic Children cannot compare to the depth of Please Save My Earth's characters, but it's still an excellent series, regardless. Just make sure you don't judge it based on its sluggish first half - its story only truly getting going in the absorbing last half of its story.
Both deal with reincarnation within a fantasy/sci-fi setting as their primary premise.
Both series deal with people with a tragic past, reincarnation, and alien life forms in a science fiction sense.
Both Please Save My Earth and Fantastic Children are both sci-fi series that deal with the theme of reincarnation of the main characters from lives past and how it affects them currently. They both have their own takes on things, Fantastic Children involves more fantastical science concepts while Please Save My Earth involves more psychic powers, but they both have the similar reincarnation theme. If you watched the Please Save My Earth OVA and you were upset at the blunt ending, Fantastic Children should serve your needs well. If you read the Please Save My Earth manga and want something similar, try Fantastic Children.
Scientists group from another planet reincarnate in our planet. Please save my earth is a shojo, while Fantastic Children could appeal more audiences.