Sonohara has just moved to a new town with his young son Tomoki. A couple of days later the "ice cream bus" comes around. It is driven by a handsome man who gives the neighborhood kids free ice cream and then drives them around while they eat it. Sonohara refuses to let Tomoki eat ice cream because it's winter, but all the other neighborhood kids get ice cream and ride the bus. The local mothers disapprove of Sonohara being divorced, and all have crushes on the driver of the ice cream bus, who started coming to the town one month ago. The following week Sonohara lets Tomoki ride the ice cream bus, saddened that Tomoki has decided he wants to live with his mother instead.
Tomoki becomes much closer to the neighborhood kids who ride the bus with him, refuses to eat the food his father makes, and doesn't want to live with his mother any more since the ice cream bus doesn't come by her house. Sonohara is suspicious as to why the bus driver would offer kids so much free ice cream. He asks to ride the bus himself, but the driver says no. When Sonohara looks through the window, he sees the kids eating from a huge mountain of ice cream, which Tomoki had spoken about previously. Tomoki is sticky when he comes back from riding the bus, but refuses to take a bath. There are puddles of something sticky all over the floor and his toys.
As Sonohara walks home on a warm spring day, he notices two young girls licking each other's skin, giggling and squealing about how sweet they taste. When he arrives home, the hallway outside his apartment is covered in sticky goo. Tomoki's friends have left their shoes outside but the house is very quiet. Sonohara goes inside and discovers that the children have melted away into ice cream, which Tomoki is joyfully licking up from the floor. Sonohara, horrified, tries to drag Tomoki away from them but only succeeds in pulling off Tomoki's head as Tomoki dissolves into ice cream. Sonohara screams as the ice cream bus arrives outside.