Ryuk gives Light a 'Love Note', with it you can make anyone fall in love with each other or another.
It works like this: if you write two people's names and draw arrows pointing to both of the names, then both of the people will be in love with each other, but if you have the arrow pointing to only one name then only one person will fall in love with the other depending on which way the arrow is pointing. You can make these two stop being in love by simply crossing both their names with a big 'X'.
Light decides to use it to make L fall in love with him, so he can get L's real name. He's writing in the notebook, but L sees what he's doing and Light panics. Light accidentaly writes himself as falling in love with L.
Light gets all 'shoujo-manga-y' on L, but Ryuk quickly grabs Light and leaves the scene.
Some Dialogue and Shinigami abuse occur.
Light gets all fangirly over L which confuzzles L. He finally confesses his love for L and L is like WTF. Light tries to kiss L, but he doesn't want none of that.
For some reason, Light wants L's cell phone so L hits him in the face with it. Light makes him a cake and then knocks L unconscience and kidnaps him.
L is at a church in a wedding dress. Light is all over L, but L gets away and bumps into Matsuda and Light's dad. Daddy Yagami doesn't look too happy and tries to talk to his son, but he gets bitchslapped proper. L asks Matsuda for help, Matsuda is knocked unconscience with a pot.
L and Light start to get all romantic but Ryuk slams into Light and traps him under a bunch of chairs. Ryuk tells L how to use the 'Love Note'. L is about to retrieve a pen from Daddy Yagami's jacket when Light tries to touch. L slaps his hand away and Light is sad and becomes angry. He hits L, but L bites his arms and takes the blood in his mouth and makes a 'X' mark over his and Light's name.
Light snaps out of it and wonder what's going on and L explains. Then, Ryuk makes L angry and smacks L with a mallet. Light burns the 'Love Note'. L and Light meet the next day and Light feels like a tard. L still has the dress.