I re-calculated efficiency of Hagakure and found out that in the end Hagakure is not worth the 3 Sen you spent on it, contrary to what the post on reddit claimed. When you consume all 3 Sens for 1x Hagakure, you get 720 potency out of it. That equals to 1x Midare Setsugekka. The only benefit of Hagakure is 1 weaponskill because Midare Setsugekka requires 1 GCD while Hagakure doesn't. The one GCD you cast after the combo is Hakaze which equals to 5 Kenki. 5 Kenki equals to 60 potency. So by using Hagakure you only benefit by 60 potency. But this benefit is when you cast Midare Setsugekka alone.

When you buff Midare Setsugekka with Kaiten, you get +360 potency benefit, which is an actual +120 potency benefit over Shinten for that cost. Substracting the earlier +60 potency benefit you got from 1 Hagakure equals +60 potency benefit in favor of Kaiten. In other words, every time you cast Kaiten + Midare you yield 60 more potency than Hagakure.