Glad you like the concept, but there's been a bit of a misunderstanding. The music in Reborn in Sin was composed by PeriTune and their work is free-use. I don't know Horizon's Gate, but they likely enjoyed PeriTune's music as much as I do and decided to use it as well. It's really cool of you to want to stand up for the devs of your favorite game, but there's no harm no foul in this instance 😊