Probably should've left this until the actual Valentine's Day but whatever
Connor - he surprises you with little things that you like all through out the day, beginning with making breakfast in bed for you. Then at the end of the day, he surprises you with a romantic dinner at your favourite restaurant.
Markus - he takes you out for a trip during the day and you both have a picnic in a field, overlooking the sun.
Kara - for Valentine's Day, you both go out shopping because that's the thing both of you equally loved. You'd both try on clothes and have the most fun while doing so.
Gavin - he wasn't the biggest believer in Valentine's Day (due to never having an actual steady girlfriend by the time the day came) but the first one you spent together, he went all out. He'd leave little love notes for you all over the house, buy you your favourite things and take you for a romantic stroll in the park at night.
North - she didn't know much about the normal customs of Valentine's Day but she tried her hardest to make you happy, despite you saying that her just being there made you happy.
Luther - he buys you chocolates and a teddy bear that's almost the same size as you. Then he cooks a lovely dinner for the both of you.
RK900 - despite doing countless amounts of research beforehand on what to do for Valentine's Day, Nines was still unsure of how to impress you. But he decided to start with the simple things, such as take you to see the movie you've been wanting to see forever, followed by lunch in a cute cafe and then a moonlit picnic at night. Finally, after you both got home, you got to share 'alone time' ;)
Ralph - he bought you tons of flowers and chocolates, and also expressed his love in a beautifully written card he made for you.
Kamski - he knew you weren't interested by materialistic stuff so he decided to make the day as simple as possible and that was what showed his love for you.
Simon - he buys you your favourite food throughout the day and watches movies at home with you.
Josh - you both go away for the weekend to a quite little cabin and spend Valentine's Day there.