I forgot the title of a certain sci-fi manga I read about a long ago, but I remember certain details such as a high school girl and a pharmacist were kidnapped from earth and are living alone on an alien planet.
Their bodies were modified by aliens to adapt to the conditions of the alien planet. They eat fruits that contains enough mercury to kill humans. In the last chapter, the pharmacist is revealed to be actually an alien.

Please tell me what title was that.

Kanaria-tachi no Fune, I think.

Yes! That is it. That is the title I have been looking for!
Kanaria-tachi no Fune, Thank you very much