On her first full day in the Tanforan internment camp, Yuki makes a new friend in the shape of Emiko Kurihara, who's there with her two grandparents. The Kuriharas live next door to Yuki and her family and, after conducting a conversation through the wall, meet each other out in the hallway.
Yuki finds out from Emiko that both her parents are dead and that she's been brought up by her grandparents. As Yuki soon discovers, the Kuriharas are a very traditional Japanese family, and Emiko's grandmother packed many small food items for them to take with them to the internment camp.
As for Emiko's grandfather, he wasn't arrested by the authorities, as he was too old. He was allowed to stay at home, but he chose to accompany his wife and granddaughter to their forced captivity in Tanforan.
As a traditional Japanese man, Emiko's grandfather has a very strong sense of familial responsibility, which explains why he feels duty-bound to raise his orphaned granddaughter as best he can, despite some pretty trying circumstances. It's a measure of his attachment to the old ways that he's prepared to spend part of his twilight years in such an unpleasant environment for the good of his granddaughter.