First meeting in 20 years! Saeba-san, meet my younger sister (Part 1)

what happens

A woman named Sayuri Tachiki approaches Saeko with a request to meet her long lost sister, who happens to be Kaori. Because Kaori does not know the truth of her existence, Ryo decides to take Sayuri on as a "client" and have Kaori interact with her to see what happens. Ryo then notices that someone may be after Sayuri. When Sayuri notices that Kaori is training with a gun, she becomes angry at Ryo and fearful that her sister may end up with a horrible fate in the underworld.