Hi, my dear! I'm glad you liked it.
Although I'm not fond of limiting the project with tags, I'll mention upfront that NTR (in the classical sense) is not present in the visual novel.
I suspect the "King's Game" scene may have confused you—in that scene, the protagonist seemingly hesitated and failed to protect the heroine because his relationship with her wasn't "warm" enough. However, if you previously expressed a desire to commit to her and she agreed, I recommend trusting her (•⩊•)
If, on the other hand, you expressed a wish not to tie yourself down with any commitments, or your relationship was so neutral that the topic never came up, there's a chance someone else might "capture" the heroine's heart (this, by the way, applies not only to Doriana) ╮(︶▽︶)╭
But as you understand, this is by no means NTR