Why is the supermarket the heart of Sasaki's routine?

The supermarket is the emotional and practical anchor of Sasaki’s day because it provides the one reliable, small pleasure amid his monotonous office life. In the supplied context it’s described as “the only bright spot” — he goes there regularly and looks forward to seeing Yamada’s smiling face. It’s nearby (so it fits neatly into his routine) and tied to his coping ritual: his trips there coincide with his smoking habit and the brief respite it gives him. When that routine is disrupted (he misses Yamada’s shift and can’t even find a smoking area), the loss is felt sharply — which also sets up the story beat where he’s invited to a secret smoking spot by Tayama. In short: the supermarket concentrates the tiny human connection and ritual comforts that break up his otherwise unrewarding days.