If you're enticed by the prospect of pregnancy, don't. It's not an ending but it's also incredibly underwhelming.
Every now and then, a hentai artist decides to make the leap from artist to game dev. Quite a few incredibly popular games on here are made by such people, with anything made by butakoma (Vitamin Quest 1 & 2, Drop Factory, Vitamin Plus aka the OG Slice of Venture) being such examples. However, the sad reality is that a good artist does not necessarily a good dev make and this is one of them.
Kishimen of the h-doujin circle Hot Mikan focuses primarily on lovey-dovey incest that ends with pregnancy and that is definitely prevalent here. A lot of emphasis--though I'm using that term lightly--is placed on building up the MC's little sister's affection towards him. Brute forcing towards sexing her will lead to a bad end. Instead, affection points (AP) can be built up by completing quests together, taking her to a cafe, and indulging in her wants and needs. That said, you could easily move to get most of the h-scenes once you get more than 5 AP.
The plot is... there, kinda like the map. It's painfully basic and simple with the only saving grace there being the high-quality CGs though that's pretty much a given with the dev's artist background. Other things that make this game a bare 3-stars rather than 1 or 2-stars is the fact that there are blatant hints towards getting erotic scenes, instant-teleporation back to town after completion of quests, and a straight-up full CG gallery in a well next to the MC's house. Sure, it's lazy as all hell but it's almost like the dev is either fully aware how mediocre it is, or put in those features because this is his first game.
I personally lean towards the latter because there are some questionable gameplay design choices throughout. Most notably being that there's a standard RPG combat system in a game where the focus is committing Alabama. There are a lot of ways they could've done to pad out the game such as having the gameplay revolve around either romancing the sister, mindbreaking her, or knocking her up in her sleep. Hell, maybe even have some mechanics which are tied to pregnancy itself such as fertility cycles, an optional birth scene or two, and/or actually have an ending involving said pregnancy instead of a boring endless mode where the MC's sister's just stuck as a pregnant chick.
All in all, it's not bad and it's definitely not good either. Just painfully mediocre with not much else that can be said that anyone else hasn't already said.