At the moment, Hokage Minato does not have a bond skill. The only new bond mysteries that the China server has is for edo minato and KCM naruto, which was released a month ago. Both versions of minato offers different types of gameplay. Hokage is more using his passive to boost the teams resistance (becomes permanent after skill broken - we don't have this yet) along side with his AOE mystery if a tagged ninja is present. Jonin is more offensive with his scalling passive and "every turn" mystery + bond mystery.

If your ninja has the "joint skills, joint skills" , it means it has a bond mystery and you need to activate it:

If you don't know the requirements of activating the current bond mysteries, here's the post about it: https://forum-narutoen.oasgames.com/page/show-post-33705-1.html