Master-Servant Vow
Shinmai v10 002
Name Master-Servant Vow
Kanji 主従誓約
Rōmaji Shujū seiyaku

Master-Servant Vow (主従誓約 Shujū seiyaku) is what exists beyond the Master-Servant Contract.


The master servant vow is the deepest subordination one could give to one’s master. It’s the ultimate form of master-servant relationship, which could only be reached between a master who’s prepared for their subordinate to belong completely to them, and a subordinate who could vow their heart and body entirely to their master.

On the other side of the unbelievable power that came with it, is a forbidden relation that could not be erased. Among those whose souls are tied together by the master-servant magic, there aren’t many who could successfully reach the vow. It’s always been seen as nothing more than a legend or fairytale.   


The vow ties master and servant together forever, and significantly boosts the power of a master as well as their servants. There are several conditions required for changing a Master-Servant Contract into a vow:

  1. The original contract has to reach its maximum possible state.
  2. Servants have to be willing to devote all of their heart as well as their body eternally to their master