With the sigh and those sad eyes, you get the impression that the master has been trying to appoint his true successor for quite some time.

Trippy. I think you did an excellent job of describing his exasperation and the pain that continuing to live is causing this man.
I’m getting a very alien vibe from what has “possessed” him. Very wicked.

Definitely unconventional. Zen maybe not, but a good twist nonetheless.

By the way, it’s spelled eunuch and the past-tense form for kneel is knelt.
I love the irony of the meditation room being so oppressive for this zen master who clearly has lost his zen.