After the events of the previous chapter, Hayate thinks that it would be a good idea if he went apologize to Wataru. Maria thinks this is a good idea, since she'd probably feel bad if things were left as they were. On the other hand, Nagi advises him to leave things be, calling Wataru weak for crying in the first place. Isumi doesn't agree, and she thinks that Hayate should apologize despite the fact that even she thinks that Wataru is weak. Hayate asks where his mansion is, and he's surprised to hear that he doesn't actually live in a mansion, but instead in the upper floor of the Tachibana Group offices. Since the location is in the city, Hayate decides that taking the train would be the best way to get there, to the confusion of everyone present. Isumi and Nagi were surprised that trains are actually common, and Maria was thinking he was talking about bullet trains. Hayate then asks them if any of them have heard of the subway, but none of them have. As he describes the subway to them, Nagi suddenly decides that she wants to check out the subway, and they all offer to come along. Outside, Maria is a little concerned about the subways, wondering if they're safe, and Hayate reassures her that they are.
Just then, Isumi disappears. They instantly start trying to find her. In the city, Isumi asks some construction workers if the hole they've dug is the subway, and she also asks if there are things like dinosaurs down there. The worker jokingly tells her that there are plenty of mysteries under Tokyo, and she suddenly disappears again. At the mansion, Nagi realizes that Isumi is going to seek out the nearest thing she thinks is the subway, and they end up finding the same set of construction workers. The workers mention seeing someone who resembled Isumi, and they head into the underground construction site. They start searching around, but Nagi starts becoming afraid of the dark. When Hayate mentions that he knows that Nagi can't sleep alone, she instantly gets defensive and starts shouting at him. Hayate says that quality is cute, and then he starts expressing concern at the shouting she did. Nagi asks why, and he says that shouting can lure out rats and agitate them. Just then, a horde of rats appears and starts chasing them. They run away, and come across Isumi along the way. Isumi tells the rats that they're being noisy, and they stop instantly. She then shows them a slip of paper, which causes them to flee. Afterwards, back at the mansion, they promptly realized that they have forgotten why they were going to ride the subway in the first place.