Porn Game: Living Together! - v0.39 by Advent Games

Meet your love interest (nameable). She’s referred to you all her life as Oniichan (relationship changeable). Affectionately, you also call her your little Sister (also changeable)!
You cohabitate in a small studio apartment. You’ll have to get along in this small area where you’ll spend a lot of time together. Through interacting with her, you build up a relationship that’s based on trust, friendship . . . and more! Talk to her and find out her favourite topics, play video games, and take her with you on day trips. Through your actions, she can come to trust you more, and, of course, you can also build her sexual attraction toward you. But be warned! You can also lose her trust in you.
Living Together! is a laid-back game intended to be played with one hand. Please enjoy this simple Oniichan game.​

Living Together! - v0.39 by Advent Games game preview

online.