@GodricKharg Ryuu didn't seem interested in bringing her back though. It was Koharu who went after her. Ryuu basically just took the attitude of "if she wants to go, let her". Then when Yuzu ran off after the entire thing with her old boyfriend coming back, he didn't go after her either. It was Koharu who went after her and brought her back. Once she was back, Ryuu didn't really do anything to try and convince her to stay...it was basically her old boyfriend who convinced her she should stay with Ryuu. Throughout the manga, Ryuu has just seemed to manipulate people just so he can get his way.
He conned Koharu into marrying him by saving her family cafe
He conned Koharu into having sex with him by bullying her, guilting her and finally playing on jealousy by hitting on that high school girl
In the flashbacks with Yuzu and her boyfriend, it seems he actively put doubt in both of their minds as to whether or not they were good for each other, and then when the boyfriend went to prison for protecting Ryuu, he move in on Yuzu.