Board Thread:Questions and Answers/@comment-19261475-20131210041114/@comment-3445779-20131211063039

PhoenixDragonSamurai wrote: Could also be a continuity error since i think that Nagi also failed to see him at times. Anothier weird thing is that Sakuya seems to be able to see Father Linn (as seen in one of the chapters where Hayate took Maria to a date)  even though she never enter the church

I'm certain the time various from person to person, but in Nagi's case she couldn't see him because she had lost the ability to after Church of Alexander Mark/Tiger's Den for Butlers was destroyed. As for Sakuya,  perhaps she has the ability to see super natural things (ghosts,demons etc....) seeing that she's always accompanied Isumi when ever she performed any exorcisms in the series.