Yes, there is believe in our culture regarding the soul.After death to make the soul/spirit calm,many rituals are done.
Yes,soul mates do exist, those who complete each other and made for each other:)
Well,I do believe in reincarnation but technically I don't.
In my view, the soul is like a battery(Power source) in our body that drives the brain and brain drive all other parts.So after death, it may be transformed into something else as we all know energy neither be created nor be destroyed ,it only transforms from one form to another.
I hope that your realistic part is making mistake and there is not only darkness and nothing. =)