tl;dr: The monster is missing. I've checked over and over along with two others. Please fix this bug! If you don't believe me, feel free to search the forums for "family secret" to see numerous other times this has happened.
So, there are four parts of the Kagerou/Oboro quest. The first three weren't too bad, although for some reason I wasn't given the shuriken I made in the Test of Weaponry. However, the last test is the Battle Test, in which the player is meant to find a monster called Family Secret in a room full of other monsters. It's meant to be difficult to find, but that's assuming it's actually there.
I've thoroughly searched this room several times since two nights ago. In that time I met two other level 99 Ninjas who were also stuck because none of us could find this monster. Yesterday one of them said he had been stuck on the mission for four days because of it! 
I've tried going through the room looking at each monster type one by one; porings, drops, poporings, lunatics, willows, and pickies. None of them were the Family Secret quest monster. I tried killing some of them just to see if it would spawn the one I needed, but of course that didn't work. I went around the room in sections trying to find it as well, running in circles around the room many times trying to find the thing. I even double checked before making this post.
When I tried asking other players about this they just told me to keep searching and that it's definitely there somewhere. Yet, when I checked the forums here I saw that this quest monster disappearance has happened before. At least two of us Ninjas who are stuck have sent Support tickets and received no help so far. Can someone please help us out? This is so frustrating! 
