Kurayami Neko no Aishikata

Yakuza, the brutally yakuza cadre, and his watchman.
Even if he had sex with Saffle, Yuji was always on the side and played a role, but he had been arguing for ten years to make him own.
On the other hand, he said, "I can't sleep only with you."
The relationship between the two, which seemed to continue like this, would change significantly depending on an event ...
Is Yuji able to catch Yuki? And why is Yuki stubbornly refusing Yuji?