Continuous and Differentiable

Ling Jin and Fu Yanjie have known each other for thirteen years. Many people have asked them: "You two are really not together?" Each time they could only say "no" and carefully observe each other. The feeling of secret love is uncomfortable, and Ling Jin has tasted it secretly for so many years. She was afraid that if she told her, they wouldn't even be friends anymore. - "Fu Yanjie, you have always been very strong in my heart. I have to work harder and stay closer to you." - "I'll wait." Concept: Two-way love is the real beauty