I think the author deserves enormous respect for not having anything bad happen to that deck. I was expecting it and feeling annoyed in advance since it is such an overused trope (losing or damaging something that isn't yours).
I am on the second chapter and considering dropping this. Do they ever come up with an explanation as to why it isn't easier to just kill the MC off to save humanity?
Even if he marries, there is still the danger of him having children with other women, after all...
The premise is weird and a bit stupid but this manga managed to grow on me.
I am a bit worried that they seem to be rushing things by Chapter 15 though.