Follow the last episode, Yoruko killed by someone unknown. Kirito saw a black robed man outside and run after him. He saw him use a teleport crystal, and then he disappears. He is teleported away. The inn is protected by the system. So they are safe in the room. Schmidt thought the person in the robe was Griselda for a ghost could easily PK within safe areas. Kirito and Asuna talked about it at night and when the food given by Asuna disappears, he realizes that something they thought they saw it, but they were actually looking at something else. So there have never been any weapons or logic that could make murders possible in safe areas. 
In the hill of cross, Schmidt beg Griselda’s forgiveness. Then “Griselda” and “Grimlock” appears and interrogate him about all. He told everything. So it’s just Yoruko and Kains and they recorded it all. Yoruko and Kains are all alive in Sword Art Online Episode 6. Because within safe areas, player HP bars cannot lower under normal circumstances. They are now on a small hill that’s close to town on the 19th floor. The PK guild “Laughing Coffin” come out suddenly and would like to kill Schmidt, Yoruko and Kains all together. Kirito arrive just in time. He saved everyone. After that, Kirito realized that the rare ring was in Griselda’s storage and when she dies, it reaches Grimlock’s storage. The order must be Grimlock. Grimlock told that because the love for previous Yuuko and killed her. Asuna point out that was the feeling of possession. They all gone and Kirito and Asuna add each other with friends. Their love story goes on. A beautiful picture!