At first, Yozo finds the idea of dying by suicide abstract and hard to grasp, perhaps because he has been struggling with depression and feelings of alienation for his entire life, so it's hard to conceive of bringing all this suffering to an end. The fact that the reality of his plan finally strikes him when he goes to pay for a glass of milk ultimately aligns with the way that mundane aspects of everyday life depress him. He thinks he’s never going to experience such a thing again, but he’s ultimately wrong, since he ends up surviving. The fact that Tsuneko
doesn’t survive, though, suggests that Yozo will be in an even worse position than he was before trying to die by suicide, since he will perhaps feel guilty that Tsuneko died and he didn’t.