Only one, personally. But I've experienced the memories of one other, and... Heard about some others in detail.

[She looks away.]

... Some of the memory shares were intentional. Usually, it was accidental, and... I don't know if it was cruelty. I hate the Echoes in charge, of course, but I don't know if that was intentional cruelty, or just... An unavoidable problem with the system.

[also, as a note: if kurama can sense these things, she's only got about half of her soul. maybe two thirds. the rest is just, gone.]