Certain FGO Girls x Male Rengoku Reader:

Plus:

Alter Counterparts x Male Akaza Reader:

The Rengoku Reader will only be paired with females who have an Alter counterpart like Jeanne and Artoria and the Akaza Reader will be paired with said Counterparts.

Rengoku (Saber):

Akaza (I'm torn between Avenger and Berserker):

Jeanne Alter Best Girl: