SFW
Doesn't do PDA at all, but only when he knows someone's checking you out when out in public.
In the privacy of his office or home, he'll get a little more comfy with showing affection.
Favorite thing to do is wrap his arm around your waist.
Bet your ass he'll duel anyone who disrespects him or you.
When he gives gifts for special occasions such as Birthdays or Anniversary's, don't expect flowers. Oh no. You'll be getting Ultra Rare duel monster cards. In a bouquet of course.
Family outings with him, Mokuba and yourself. Usually going to Kaiba Land and running around with Mokuba until he's content.
NSFW
His favorite place to pleasure you would have to be his office especially with the windows wide opened.
After every victory he gets either in dueling or business, be prepared to get a good pounding.
Loves it when you ride him, it not only gives him total control of your body, but it gives him the best view of you.
Gets a bit rough if he's had a bad day, so bruises are to be expected on those days.
Always does aftercare in some shape. Most of the time it's taking you in his arms and stroking your hair and back to soothe you.