dunno.... That Kisume is a bit of a loose cannon sometimes.
And the doors to the outside cannot be opened without the key that only I have...
Which means that no one could have come in from the outside!
Therefore...The killer is one of them!There has only been 4 people in this house...From what I can see the killer must be skilled at handling poisonThis looks like a murder with poison...Reimu has died without context...Oh no!