This is a re-conceptualization of Something Unlimited in a new engine with a rewritten story, entirely new mechanics, and repurposed, edited, and custom assets. ST is a true trainer game first and foremost, focusing on user choices in capturing, training, or wooing heroines and villainesses.
In order for you to be able to install this game, you need to enable (allow) installation of applications from unknown sources (Unknown sources) in the phone settings. Usually this item is in the Security section