The Butler, Toppling is Chapter 163 of the Kuroshitsuji manga.
Summary[]
After Ciel and Mey-Rin have finished their meal, Sebastian brings them their tea—Harrods' oolong. Over tea, Ciel then repeats his question whether Mey-Rin wishes to work at Phantomhive Manor as his maid or she would rather spend her life running away from Qīng Bāng.
One more time, Mey-Rin expresses concern over her suitability as a maid, but after Sebastian reassures her that she does not need any qualifications and that he himself was not a butler in his previous life, she accepts Ciel's offer. She and Ciel seal their contract with a handshake, and Ciel asks her what her name is as "Owl" cannot be her real one. Mey-Rin briefly recalls her deceased childhood friends—Jan and Hao—before she tells him that her name is "Mey-Rin."
Afterward, Sebastian guides Mey-Rin to her room. On the way, Finnian approaches them and runs into Sebastian with his full strength, knocking him down. He cries that he has once again destroyed a shovel—the fifth in the last three days. Then, Finnian notices Mey-Rin and asks if she is a guest, and when she tells him that she is the new maid, Finnian joyfully introduces himself and expresses his hope that they will become friends. They shake hands, but Finnian squeezes Mey-Rin's with too much strength and receives a scolding from Sebastian. After all, Mey-Rin needs her hand as a sniper.
Mey-Rin is appalled that Sebastian would tell a child so nonchalantly about her former occupation; however, much to Mey-Rin's confusion, Finnian is only amazed over this fact and tells her that they will, from now on, kill their master's enemies together then.