L Lawliet was with Light Yagami. He was suspicious of him being Kira still. Light shinigami Ryuk laughed (L cannot see his shinigami). You walked past them writing down something and Light noticed and looked at you. You kept walking and Light's Shinigami saw yours but you're one was only white and brown gold. L looked at light confused. "is something wrong Light" He said. Light replied. "no no.. let's just walk this way instead" This is when they started to follow you without you realizing it.