Hachi waits for his owner every day, while sleeping in the rail yard at night. He is befriended by Carl, Jasjeet (a hot dog cart vendor who used to give Professor Wilson his coffee every morning) and other regulars around the station. Hachi's loyalty is profiled in the local newspaper, and after seeing the article Ken visits Hachi and offers money to Jasjeet to pay for any expenses for the dog, but Jasjeet declines it saying everyone in the station square will take care of Hachi. Cate comes back to visit Parker's grave on the tenth anniversary of his death where she meets Ken. Walking past the station, she is stunned to see a now-elderly Hachi maintaining his vigil. Overcome with grief, Cate sits and waits for the next train with him. At home, Cate tells the now ten-year-old Ronnie about Hachi. Meanwhile, Hachi continues his daily walk to the same spot in front of the train station. One night a train arrives off-schedule, while Hachi was about to sleep, he follows the train and then sits on his usual spot waiting for his owner, which was his final day when he recollects his life with his master. He then imagines Parker coming out of the station and the two greeting each other. In reality it was Hachi dying and reuniting with his beloved master in heaven. Hachi is last seen lying on the snow, alone and still.
At the train station, Hachi waits patiently as the train arrives, but there is no sign of Parker. He remains, lying in the snow, for several hours, until Parker's son-in-law Michael (Robbie Collier Sublett) comes to collect him. The next day, Hachi returns to the station and waits. As time passes, Cate sells the house and Hachi is sent to live with her daughter Andy (Sarah Roemer), Michael, and their baby Ronnie. However, at the first opportunity, Hachi escapes and finds his way back to the station, where he sits at his usual spot. Andy arrives and takes him home, but after seeing how depressed the dog is she lets him out to return to the station.
Back in his classroom, Ronnie, forms his conclusion why Hachi will forever be his hero. Ronnie's story which has clearly moved the class, with some students holding back tears, even those who had laughed at the beginning. After school, Ronnie is met coming off the school bus by his dad and his own puppy, also named Hachi. Ronnie and Hachi walk down the same tracks where Parker and Hachi had spent so much time together.
The closing cards reveal information about the real Hachikō, who was born in Ōdate in 1923. After the death of his owner, , in 1925, Hachikō returned to the the next day and every day after that for the next nine years. The final card reveals that the real Hachikō died in March 1935. A photo of a bronze statue of Hachi is situated in front of the Shibuya train station at his sitting spot which was the last image shown before the credits roll.