Sirius Romanée-Conti/Relationships

Petelgeuse Romanée-Conti
Sirius was in love with Petelgeuse. However, when Subaru defeated him and met Sirius, she mistook Subaru as being possessed by Petelgeuse because of the Sloth Witch Factor residing in him. She loves Petelgeuse to the point she would absolutely be willing to scorch Satella just to get Petelgeuse's attention and love.

Emilia
Sirius strongly resents Emilia due to her similarities with Satella. She is blaming Satella for Petelgeuse's obsession with resurrecting the Witch, hence she expresses abnormal and unhealthy amounts of hate and disgust towards Emilia, even though they have no prior acquaintanceship with each other.

Regulus Corneas
Even though they both share the titles of Sin Archbishops of their respective sins, they show hostility towards each other. Sirius has bombarded Regulus with slurs numerous times, calling him a "damn insect" more than once. Despite their clear hatred and animosity, they are willing to cooperate if their Gospel orders them so.

Natsuki Subaru
Sirius mistook Subaru for Petelgeuse in his third Arc 5 loop and showered him with her twisted love, meant for the deceased madman. She isn't aware that in actuality, Subaru was the one who killed her "husband" and is currently in possession of the Witch Factors of Sloth. Having said that, she was unwilling to listen to Subaru's plea to back down and leave the square as she thought he was trying to get rid of her.