Yami watches Serena and her changed mood. There was a saddened look on Yami's face, knowing what Serena was most likely thinking about. "He was. His condition was more serious than we anticipated." He explains. 

Marik looked to Ishizu. "If I remember right I taught him what you taught me. We had started small, learning to harness it before we started sensing it, then I believed it varied on what one was capable of."