In the latest episode of the Xbox Two podcast, Windows Central journalist Jez Corden discussed why Xbox has rejected some games in recent years, including Gal Gun.
I've spoken to a lot of people who used to work at the company or who work there now, trying to figure out why certain games were banned on Xbox. Among fans of a certain genre, especially anime dating sims, there's a conspiracy theory. Microsoft has long had a notoriously empty library: such games are available on PlayStation, Nintendo, and Steam, but not on Xbox.
The community suspected that Microsoft was blocking these games. It turns out that it's probably not that far from a conspiracy theory. Apparently, there was a person at Xbox who hated anime games and rejected them. I've heard about this, but I treat the information with caution, as it's just an industry rumor.
According to Corden, after a change in leadership, some previously rejected games began to receive approval. He agreed with the assumption that it could have been an abuse of power by one person.