Gonna throw this post in this thread too. It's not exactly focused on fisting but the following games all have some great anal content (especially ATM - completely anal focused game that i've already mentioned on this thread). Really is a shame there aren't more games done well for this niche. Fully recommend all of the below, although Hero Party requires some extra patience as it is a hardcore corruption game.
Insight of You (You train a total bitch into a complete anal slut that wears a massive buttplug the whole time - great game)
Third Crisis (Probably the best game on this site. The Peitho route has some serious anal toys going on)
ATM Adventures (Really really really kinky and Completely Anal Focused. Take a look but you had better have unlocked some serious fetishes for this one).
Nympho Tamer (Dominate sluts into being even bigger sluts. Plenty of anal stuff)
Hero Party Must Fall (Great corruption game with good anal stuff later. Real slow at the start though)
Hitomi's Sick Pleasure (Renpy VN - Mother gets corrupted NTRing her son. That shit ain't really my jam but the scenes were hot enough to persevere with it. Lots of anal stuff)
Also if you're up for 3d animation. Check out Breaking The Quiet. Very serious anal stuff with a horse called Brutus - there's like 5 parts each about 20 minutes long or something.
Hope this helps! (ya fucken pervs)
