How the hell does sex have to do anything with uplinking a magic circuit with eachother
Err I think it had less to do with a magic circuit than raw magical energy.
Or you can think of it as a direct connection.
List of VNs:
G Senjou no Maou (prepare to feel horrible about yourself though)
Anything by Key (only played Clannad and Little Busters! myself)
Can't vouch for these but: Anything by Type-Moon?
Again, haven't played any myself but the stuff by Leaf are apparently good too. White Album and ToHeart2 come to mind.
Oh and obligatory Katawa Shoujo
Chuckles were had: