You've probably already played this...
But at least it's on android via some... annoying steps.
If not, would definitely recommend. 8/10.
It is worth noting that it works like shit on smaller phones with inferior hardware, might be good to get a tablet phone to play VNs, like this:
The phone above is a pretty low-end tablet phone. Lower $200ish price bracket. I use it myself, and it's not bad. Decent speed and hardware for the price, though mainly because I got it at $130, due to a friend working where I came in to buy the phone at the cricket store.
That aside, there's also Sepia Tears, but it's kind of old-schoolish and shitty in the graphics department, and the story is pretty generic.
As for other VNs on the android - I have looked, as an Android Tablet-Phone user myself, but have yet to find any others.
A lot of memory space is required for Katawa Shoujo on the phone, be prepared for that.
Katawa Shoujo and Sepia Tears are both free from their respective sites.