Stray Incubus is a choice based novel featuring an incubus and his harem of sexy ninja girls.
The game is a visual novel with mostly opt-in/opt-out choices throughout. However, there are currently two significant moments where you can dramatically shift the story through the MC's choices. While the consequences for these choices have yet to be seen in the story, they could be quite significant in the long run.
There is a stat screen which keeps track of how your decisions influence the girls in the game, but it doesn't appear to dramatically change anything yet. The choices for influencing the girls appear to be yes or no at the moment, so the only way to lock yourself out of content is self inflicted. There also appears to be no penalty for pursuing all the girls.
The story starts out pretty rough honestly. It has a real lack of any story arc so it feels like things just happen however and whenever the author wills it. The characters don't have much in the way of motivations and kinda just follow along with whatever harebrained plot happens next.
That said, after a rough start, things get better when the main character decides to join the ninja school. The various mission he and the sexy kunoichi go on pull the plot together into some semblance of order, though it's still kinda nebulous as to whether there's an overarching plot. It's not flawless, but the individuals missions are kinda fun, in a silly naruto-esque sort of way.
None of the characters are supremely interesting, but none of them are completely boring either. Most of the girls have a scene or two of solid focus and there's some decent banter between them and the MC. It also appears the game will have a handful of girls that are tied to the mission locations rather than the ninja school, meaning they'll feature and then pop out of the story, which is a bonus in my opinion.
I definitely can't deny that the game is pretty. The girls have nice designs and some great outfits and there's even some fairly well put together scenery. The sex scenes aren't ridiculously common throughout the game, but there's enough to keep you entertained. Some of the scenes are pretty damn hot. It's definitely a good utilization of the software.
Overall, Stray Incubus isn't a bad game, but it can be difficult to get through the rough opening. If you can deal with the random stuff happening through the early portion of the story, there's a rather fun and sexy romp hiding deeper inside. It's worth a shot if you wish Naruto had more porn.