As the developer states, its a very short game. This one is structured for a quick, and linear experience. Being a Ren'py game, you could almost guess where you would have some QTE/ decision making options IF the author decided to include them. The renders are great, The sex scene is short fun, and the end result shows this type of game/ idea has potential if the author decided to continue.
With that aside, personally I feel the game is too short even for a test/ demo, due to its pacing. There is more build up in the timing it takes for introduction of the scene, and the transition into the problem scenario compared to the ending playing out. The last few lines were so cut and dry it's like slamming the brakes as soon as you reach that nice driving speed. Had the author played out the final scene a bit better by writing more details in general I think it wouldve brought the game to an end with much more ease since its just a standalone path. Maybe more involving being dragged/carried away, or the progression of the pregnancy. Perhaps his semen or the pregnancy effects her mind like an aphrodisiac, bending to his will and thats how he knows she is now his. She couldve adopted a maternal mindset due to this scene. Perhaps its a mindbreak and more time passes. She could even escape but now feels more influenced by this event. An itch at the back of her mind wanting to return, polluting her thoughts and emotions but she continues further into the temple anyways. Followed by a "To be Continued?".
Anything that would wrap up the scene allowing the author's audience to possibly want more. Tomb raider can go in so many directions. From Mercenaries/Tribesmen, Animals/ Mythical Creatures, Supernatural/Deity, etc. Just up to the author to choose.