When reaching level 86 as Ninja you learn Hollow Nozuchi which is an action tied to Doton. However there is no trait associated with it nor does it show up in the text box when leveling up. I consistently check my actions to know what's added regardless, but not showing "You learned Hollow Nozuchi" or even a trait labeled something like "Doton Mastery" with a small description. it is quite easy to miss this action even existing as ninja.