So, looking at how censorship was a big factor for his departure - while still going to work on console games at a different company/still working on the series anyway as a Producer...
My speculation/pure guesswork is that the censorship debacle - which presumably had not just individual impact on his project, but company-wide change in content policy - might have made him feel that Marvelous does not value his creative inclinations and passion as a creative and an employee.
Where instead of the parent company supporting him and defending the freedom of sexual expression within the work - they instead bend their knee to Sony and made that a company-wide policy for all current and future projects.
If he doesn't feel valued as an employee, then there's really no longer any reason or attachment to stay at the company.
