Disclaimer: I don't own Death Note.
Misa bakes Light cookies for Valentine's day, she wills all of her love into them and weighs everything twice. It takes hours for her to get the heart shapes just right, but they are for Light and she wants them to be perfect. She wraps them into two layers of tissue paper.
Light accepts them with a nod, bites one, tells her they're delicious, then puts the other half down and turns back to his work. L takes the rest, he doesn't say thank you, but he smiles when he eats them. 'Maybe she put too much sugar in,' she thinks, 'Light doesn't like sweet things."
Misa always gets more cards and presents on Valentine's day than any other day of the year. She never opens them all, but this year is different, Light hasn't given her a card, and she knows that he would never forget anything like that. So this year she opens every one, it takes her over a week. Matsuda helps, but ends up asking Light. He returns three hours later with an envelope. He tells her the post office lost it. She kisses him on the cheek and laughs.
"They forgot to stamp it, no wonder they didn't send it." It's a beautiful card, handmade and covered in calligraphy. She keeps it on her bedside table.