I've uploaded a new build of the Android version just now: v1.2.4
This version has the different language options displayed on the main menu screen.
I've given it a quick test on a few devices and Spanish seems to work okay. But it's worth noting that the game itself is a bit demanding compared to other VNs (it runs at 1440p, so it uses more system resources). That might cause it to crash if you're running it on a phone without much RAM, or if you have a bunch of other things running in the background.
Anyway, please give it a go and let me know if you run into any issues.