Ten years ago, Seiji went to City A along with his other classmates for a field trip. It was an overseas field trip only rich people could afford. Apparently, he studied in an international school when he was in middle school. At that time, their teachers wanted them to learn about cultural differences and the choice of city that the parents chose for their children to explore was City A.
Seiji was one of the most excited students at that time. His father was busy managing their business after his grandfather retired from the business world. His mother has to help his father as well so, in the end, his grandpa accompanied Seiji during the field trip.
You can say that Seiji was spoiled by his grandfather very much but he wasn't a willful and disobedient child. He was sensible and he would always weigh things down if it's part of what he needs or what he wants.
He would always listen to his parents and his grandfather.