There's a lot going on in this chapter, it's all but directly confirmed that Lady Blaze was Sen's mom, but there's some interesting stuff going on with the salesman too.
The salesman is obviously a genius planner, not only did he coordinate the Parasite Vampire to take over Lady Frost, but also in how he orchestrated the events with the Virus Monster. It makes you wonder though, what's his real motive? He seems to have something bigger in mind, the "company" he keeps mentioning seems to be highly respected by monsters, both Dake Naldi and the Parasite wanted a place in it and now they seem to be doing something with Bank Drivers. They've probably already gotten a few normal drivers, which is why he wanted Sen's specifically.