Iirc the energy required to break down water into hydrogen and oxygen is greater than what burning the mixture produces, but in theory solar power might be a viable option to a certain extent.
Efficiency/viability would probably be nonexistent without some sort of miracle catalyst for the breakdown process.
I imagine in this case, it’s for the intellectual property; i.e. the octopath traveller name and trademark. Which probably means they intend to develop future products under the OT name.