Pretty alright ending all things considered, though it felt a bit rushed. Also, I personally don't know what I would've thought about Yuma actually getting Hana pregnant, but that question should've had at least some kind of a conclusion after all of the foreshadowing, in my opinion. For example, there was that one time Tatsuki got scared that what if Hana was asking him to cum inside of her because she was already pregnant with Yuma's kid and tried to fool him into thinking it would be his and Yuma also constantly mentioned how he wanted to impregnate Hana during sex, even during the epilogue scene. Then... nothing came out of that in the end. There could've been a scene where they discussed that possibility seriously (outside of the play) and then decided whatever Fallen wanted to go with, but as it is now the topic just never had a conclusion one way or another.
Also, while it's true that Hana went behind Tatsuki's back, it's still a stretch to call it actual NTR since, as people guessed, she did it to surprise Tatsuki because she knew it would get him off. In the end, they all decided that this is what they want together without anyone being stolen away without approval.