I left Cassidy as a slave or pet when Dwayne got capped. Never ran into a problem with Shiori. Try breaking up with Cassidy then immediately apologizing so she is an ex-girlfriend and see what happens.
The difference in my situation would be that I accept her as a girlfriend and not a sex slave, and I don't know if it is on purpose that the relationship with her cannot be ended, and that prevents me from moving forward in the event of the picnic with Emma.
The icon of the option to terminate the relationship is not shown also, I tried in different locations if maybe it appeared but it did not appear either.
