The core to yandere logic is assumptions, and Ekam will assume that you will come with him, whether willingly or bound. After all, why would "you" choose to chase him through that portal if "you" didn't want this?
Thank you for enjoying my game, and I have wonderful news if you want more! There's actually a continuation of this game here, a Part 2 if you will.
Full link also here: https://atelierursine.itch.io/penetrate-the-veil-spoken-hearts
It's not that much longer — around 4k words — but there are four happy endings with Ekam.