Koei Tecmo will be releasing the Ninja Gaiden trilogy for Nintendo Switch and other platforms, which is a boon for action game fans who want a high level of challenge. However, some versions of the trilogy will only include Ninja Gaiden Sigma 1 and Ninja Gaiden Sigma 2, revised versions of the original Xbox title meant for other platforms like the PS3.

Why is this so? And why isn’t Ninja Gaiden Black included in the trilogy as well? According to Koei Tecmo (via Famitsu & Kotaku), developer Team Ninja could not salvage the remaining data to port the older games into the collection. Here’s what Team Ninja brand manager Fumihiko Yasuda said:

“For me personally, Ninja Gaiden II was my debut, and so I have a deep feeling for it. But there’s another reason for this choice. To be honest, there are only fragments of the data that remain. We couldn’t salvage them. However, when developing Sigma Plus and Sigma Plus 2 [for the PlayStation Vita], we got as much of this kind of data together as we could and organized it. Because we use utilize that is the reason why we selected Sigma.”

At the very least, you can still play Ninja Gaiden Black and Ninja Gaiden 2 on Xbox Game Pass, if they make their way onto the service again.