|Well, it depends, for L, it's pretty easy, just need a long sleeve white shirt and simple blue jeans, but he is about 95% barefoot, if you are okay going barefoot at cons, then L.
For Light, you'll need a black or white long sleeve collared shirt, red tie, black jeans and shoes. If you aren't okay going barefoot for L, then Light would be best. I too am cosplaying Light, I'll have a black long sleeve collared shirt instead of white. Plus you'll carry around the Death Note and a pen, which is what will I do.
Good luck on your choices!
Pokémon Trainer Red [Pokémon Adventures]
Lelouch/Zero [Code Geass]
Death the Kid [Soul Eater]
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