The Hierophant Social Link is one of the earliest bonds you can make in Persona 3 Reload, represented by the elderly couple that owns the Bookworms store in Iwatodai Strip Mall. This is by far the easiest non-semi-automatic Social Link in the game, but be careful not to neglect it.
Persona 3 Reload Hierophant Social Link Guide (P3R)
The Hierophant Social Link can be started from 4/25 onward by visiting Bookworms in Iwatodai Strip Mall. Your classmates will inform you about its reopening during the morning, so use your time after school to meet Bunkichi and Mitsuko Kitamura there. You can stop by the bookstore every day except Mondays, including holidays.