To be honest i have not seen much in this genre other than btoom, lets lagoon. I would prefer the survival go be like uninhabited Island with preferably 1 dude and 1 girl, doesn't have to be on an Island though, could be in space for all i Care. If the main couple kiss or have sex that is a something i would prefer also. If by the last chapter all that happens is a small confession and a tiny kiss i kinda feel cheated.

Suicide Island This manga is relatively long, graphic, but there's more than one guy and girl. The story is based of several people that failed to attempt suicide are sent to an isolated island to do whatever they want, whether it's to live or die. The story is a fight for survival, and people go against each other.