Complex sentence: Sometime after leaving the Phantomhive manor once the murders were solved, Irene and Grimsby broke off their relationship and is currently dating (albeit secretly) an actor from a rivaling theater company.
Split into simpler sentences: Sometime after leaving the Phantomhive manor once the murders were solved, Irene and Grimsby broke off their relationship. She is currently dating (albeit secretly) an actor from a rivaling theater company.