[With a nod, Gundam focuses on their hands and gives this some thought before speaking.]

Through the hardships we'll face here, whether they be changes or taking our freedom back, I will remain your pact partner. And, upon returning to our world, no matter what we are faced with upon waking up, I will remain your pact partner, and nothing can break this bond. I promise.

[There. That's simple and elegant and gets the point across!]