Like a Dragon: Infinite Wealth

This is a Kiryu thing, and will require you complete special substories known as Life Links. It's there in the description. There are eight Life Links in total, and the first one will be marked on your map as a book with a pencil. The next four after that can be completed in sequence, but there are also three that require reaching Level 7, 8, and 9 in Kiryu's Awakening stats. Complete them all and you'll earn this.