Watts and Cinder had a very antagonistic relationship. Watts was shown to have looked down on Cinder after she was defeated by Ruby. He greatly enjoyed tormenting and angering her in volume 4, especially since she was unable to speak as a result of her injury. It is assumed that they had a preexisting rivalry prior to her injury as well. It can also be inferred that their mutual disdain of each other was likely a reason why he didn't provide a prosthetic arm for Cinder, leaving Salem to replace it with a Shadow Hand. In "Dread in the Air", Watts was disappointed after discovering that Cinder's voice had recovered.
This in turn makes Cinder tell him to shut up. In volume 5, Watts worked with Cinder to pressure Raven into having Vernal use her Maiden powers to open the Relic of Knowledge's chamber. When Cinder agreed to Raven's demand for her brother's death, Watts warns Cinder of her intentions to use this as an excuse to get revenge on Ruby. However, Cinder dismisses him and burns his hand in response and tells him to go back and play with his toys. Watts was also stunned into silent disbelief in volume 6 when it was revealed that Cinder was still alive.
Later after his capture and imprisonment in Atlas, Salem orders Cinder to go and rescue him from his cell and have him assist her in locating the Maiden. Once Cinder successfully locates Watts and rescues him from his jail cell she carries him on her back and the two fly away. In "Ultimatum", Cinder threatens to kill Watts by dropping him to his death after he revealed the virus he implanted in Penny was set to cause her to self destruct after she opens the vault. This made Cinder enraged due to the fact that this would make her unable to retrieve the maiden powers. She then impulsively grabbed Watts by the collar and dangled him from the top of the building they were on in order to force him to listen to her.
Firewall is a rarepair within the RWBY fandom, mainly because Cinder and Watts had a very tense relationship and didn't like each other. Also there was quite a noticeable age gap between the two. The ship sank after Cinder indirectly killed Watts in volume 8. Some people liked to believe that the two had more of a mentor/student relationship than a romantic one. It has a small fanbase on Tumblr.
- "Firewall" comes from the fact that Cinder has a fire based semblance and Watts is very technology savy. Hence the firewall.