Ushio is the only child of Tomoya and Nagisa. She is shy, timid, and strong-willed. Ushio inherited her mother's weak constitution. Her name means "tide", which is related to her mother's name Nagisa which means "beach".
Nagisa lost her life giving birth to Ushio. Tomoya fell into depression and Ushio was given to the care of Sanae. Sanae taught Ushio that she was only allowed to cry in a bathroom or in Tomoya's arms. When Ushio was 5 years old, Sanae invited Tomoya to go on a holiday with Ushio in the countryside for 3 days. Sanae and Akio then disappeared and requested Tomoya to go ahead with Ushio.
Initially, Tomoya was distant from Ushio and she tried to get close to Tomoya. Tomoya spent the first day waiting for Sanae's and Akio's return and decided to go ahead on the second day. Sanae had already bought the train ticket and planned their itinerary. On the way to the countryside, Tomoya got off a train stop to buy a toy robot for Ushio. Tomoya pondered about his cold disposition towards Ushio and wondered if he is a bad father for Ushio.
The next day, they took another train. Ushio asked about Nagisa and Tomoya refused to answer. They got of on the last train stop and they found a flower field. Ushio played around the field but lost the toy robot. She insisted on searching for the robot. After Tomoya returned from talking to Shino, Ushio was still searching for the robot. She explained that she treasured the robot because it was the first gift that she received from Tomoya. Tomoya promised to take care of her as her father.
On the train back, Tomoya told Ushio about Nagisa and he was finally able to open up to Ushio. Back at the Furukawa bakery, Tomoya thanked Sanae and Akio for taking care of Ushio and requested to retrieve Ushio from Sanae's care.
The following day, Tomoya visited his father, Naoyuki with Ushio. Tomoya relayed Shino's message to him and thanked him for his effort in raising him. Naoyuki was happy to see Ushio.
Tomoya then sent Ushio to the kindergarten and they met an enormous Botan and Kyou, Ushio's teacher. Kyou reported that Ushio is a good kid. During the holidays, Tomoya and Ushio visited the Furukawa bakery. They met Kouko and Fuko and they introduced each other. Fuko liked Ushio and became attached to her.
A week before the kindergarten Sports Meet, Ushio came down with fever. Tomoya took leave from work to take care of Ushio and phoned Sanae for help. The doctor revealed that Ushio was suffering from the same illness as her mother, Nagisa did. Ushio wanted to go on another trip. The apartment rent continued to accumulate and Akio offered to pay off the rent for Tomoya, which he declined.
Tomoya had ran out of money in Winter. Tomoya invited Ushio for a trip. Ushio passed away in the cold and Tomoya died soon after.
In Tomoya's last dream, Ushio is revealed to the girl from the Illusionary World. She requested Tomoya to obtain all Light Orbs to change their fate and sent him back in time.
Nagisa survived the childbirth and Tomoya bathed Ushio under Sanae's guidance. The credits roll implied that Tomoya, Nagisa, and Ushio visited Shino. Fuko discovered the girl from the Illusionary World lying under a tree.