This app is on the App Store (Apple) and I really enjoyed playing it. There's multiple seasons to pick from and you always get rewards so you don't have to buy anything if you just log on consistantly.
I'm currently playing season 3 (out of 5) and its really good so far. There's 10 chapters with multiple parts so they're decently long.
Here's some pictures of the app.
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Link: https://itunes.apple.com/us/app/moe-ninja-girls-visual-novel-for-anime-fans/id1176808760?mt=8