Before becoming Julie's Duo, she and Tooru both got along great, eating lunch together and training together so often that some students thought they were dating at first. When Tooru was about to pair up with his friend he learned that Julie didn't have a Duo and he partnered up with her instead. After becoming a Duo, instead of the bond falling because they had to sleep in the same room, they instead grew closer. So much that Julie doesn't mind walking around with only a white shirt on. Their relationship is so in sync that when fighting they can tell what the other wants to do without even speaking as shown when they battled against Lilith. It is also shown that Tooru cares a great deal for Julie when she was shot. He raged to such an extent that Julie had to calm him down.
Tooru's and Lilith's relationship was bad at first when Tooru rejected to break his Duo with Julie and team up with Lilith but as the story progressed Tooru started to trust her more, what's more there both rare types which makes them get along more. At the beginning Tooru hated Lilith for shooting his friends but later when he learned of her past he wanted to help her and because of this Lilith falls in love with Tooru and wants to marry him and she even calls him darling all the time which makes the other girls mad/