When Diego started to understand the meaning of 'lover,' Vincent constantly warned him not to mess around with a woman's feelings or have sex with her to satisfy a man's drive.
If one day Diego had a daughter, let karma not haunt him and would target his daughter. Moreover, Diego had an older sister he loved dearly, and he didn't want to see his sister suffer from being abused or toyed with by a lustful man.
When he was in a relationship with Yuna, Diego never did more that could make him get out of control. He also never asked the girl to stay with him or sleep with him.
He respected Yuna as a woman and never looked down on her. Therefore, he became confused and furious when he learned Chleo was marrying under threat, yet his father gave his blessing.
He couldn't understand Vincent's way of thinking about letting his daughter be taken away from America. And he felt angry with himself for not being able to do anything to help his sister.
