Well … I found this one, I don’t know it, but it looks interesting
Edit: Apparently it works with microtransactions, but, I don’t have enough space on the cell phone to check if the system is abusive or not .-.
Edit 2: So, I found out I was wrong and I ended up having space on my phone to download cytus 2, and I ended up taking a quick look … Actually, the game has microtransactions (of the 16 characters only 6 are available), but only just them already has reasonable content for you to enjoy for a few hours.
In other words, the game is not completely free … But, even if you don’t buy any of the DLCs, I think it’s a good opportunity to get to know the genre and kill a few hours