These girls actually have names. It's in the introduction section on the DLsite page. (The source link)
From left to right: Shino Aikawa (The girl with the hair bow) Mia (The girl making the peace sign) Sayuki Shirase (The petite girl) Natsume Houjou (The ponytail girl) Yua (The girl with her arm behind her head)
I'm obligated to choose whenever I see the 'take your pick' tag. Got dibs on Sayuki. And yes, I know, Mia and Yua do not have last names, just look at the site yourself. They legit have no last names.
EDIT: Oh, also. The product in the source link is an ASMR product.