The father of the most beautiful daughter wants to say "son" to the hero because the father has been fascinated by perfume and thinks that even the murderer of his daughter is like an angel, so he can't help but ask his son to express his love for him.
Because the protagonist can't love others and be loved like a normal person, because the perfume deifies him, he has lost his original feelings as a man, so he is obsessed with the first girl and cries bitterly. If he can still have love for the opposite sex before killing the first girl, he will not be a person after killing him. The reason why he cried is like a vampire who lost his original human feelings and basic human feelings. He couldn't get back to the beginning, so the protagonist cried. This is also one of the reasons why the protagonist committed suicide. But personally, I think the main reason for suicide is that he made the most perfect perfume in the world, and the ultimate goal of life was achieved, so he could not live as a normal and bound human being. We know that all the people related to him died in an accident.