I am. She was under contract with my Master at first but when he offered her to me, we formed a contract ourselves.

It's more of a spoken thing really. And I couldn't help it, she was awfully cute back then~.

[How she summoned them, well. There's a moment of hesitation again but in the end Nagi reaches into her jacket and pulls out a long silver tube bearing a ring on it's end.]

When not in service, demons that a Summoner had formed a contract with reside within these tubes. A Summoner may thus summon the demon whenever they like from them.