Kioku Inpei
Memory Concealment

Only a small part of the Sohma Clan knows the secret of the 12shi. Using Hatori's ability to manipulate memory, the clan has managed to prevent the having the secret leak outside. Young Yuki's friends had their memories of him blanked out after they unfortunately saw Yuki transform. Momiji's mother had her memory changed and believes Momiji to be another family member's child. Also, Hatori himself, erased his girlfriend's memories of himself. The one to give the order is of course, Akito.

From Vol 15:
Hatori's ability to supress memory isn't special to him but is a technique handed down through his family. It's pure chance that Hatori was born into that family and learned the technique and also happened to be possessed by one of the 12shi spirits.