Mattias would have fallen asleep on his couch, with the killer notebook on his chest. He would yawn rather audibly, clicking on the television, it would already have been on the news channel, as that's all he ever watched.
His eyebrows would perk up, the story being covered would pertain to recent killings not unlike those from the Kira case.
"...Shinigami need to stick to their damned realm, this world is mine..."
He would roll off the couch, clutching the notebook, he would jump up and head towards his computer. Logging in, he would set the notebook next to his keyboard.
"Starting to look like this vicious game will never end..."