These three stats are the only ones you cannot change. You are automatically given an age and birthday when you first join the game. Other players will have a different age and birthday. Your rank is earned from joining a Family in-game or creating one. (25k yen)
The Trello still shows the old ¥25,000 founding price. The current cost is ¥250,000 to found, ¥100,000 to rename, and ¥10,000 per extra seat from 10 up to 50 members.