Fafnir/Relationships

Asia Argento
Asia made a contract with Fafnir when Azazel decided to cancel his since he saw Asia's potential as a Dragon Tamer. To establish the contract, Asia has to pay the price her panties as offering. Although little is know with their current relationship, Fafnir seems to like Asia to the point that his perverted side is shown and will protect her from harms way if needed.

Issei Hyoudou
In Volume 14, at fiirst Issei thought of Fafnir as an amazing Dragon King when he was summoned by Asia to help recover Ddraig's mentality back. To his dismay, Fafnir was a pervert seeking only panties from Asia in exchange to help Ddraig to recover but seems to be pleased although regretful that the dragon will protect Asia from harms way like how he protected her from Grendel's fire balls.

Azazel

Little is know from their relationship other than Azazel making a contract with Fafnir to help him in his Sacred Gear research. He eventually developing an artificial Sacred Gear with Fafnir sealed in it but decided to cancel the contract by Volume 14 so that Asia can establish a contract with the Dragon King with Ophis being the mediator.

Dragons
Ophis Ophis at first becomes the mediator for Asia to establish a contract with Fafnir but eventually sees him as an ally in Volume 15 as she believes that She, Fafnir and Rassei can now challege Great Red.

Ddraig
Ddraig doesn't seem to like Fafnir. In Volume 15, he even denied Fafnir's existence when Issei brought up how perverted the Dragon King is.