On the first day of officially working with L -- or, Ryuuzaki, as he told them to call them -- Matsuda had acted very much like the intern L initially thought he was. He scampered around getting records, making calls, fetching video tapes, retrieving lunch, making coffee, serving said coffee, and when he wasn't running around he was listening as L talked to the Chief or Aizawa or, sometimes even Mogi.
And on that first day, Matsuda had made the grave mistake of giving L black coffee. Chance that Matsuda was an idiot: 99.98. L was only giving him that .2 because, part of him reasoned, Matsuda didn't know how he liked that coffee. Still, the larger, sugar-deprived part of him made it a point to sulk childishly and stare pitifully at that mass of too dark liquid.
Being the genius he was, it didn't take long for him to figure out that the coffee would not suddenly become sweet just because he was staring at it. So, with a sigh, he got up and went in search for his beloved sugar cubes. Finally finding them, he lumbered back to his chair, dropped in some cubes, and finally drank his coffee.
Only to find it was cold.
Chance that Matsuda was an idiot: 100