Complete Sophia's nine dependent tasks, 10 heart, a double bed and a ring, and talk to her after the exchange festival. Press L\R (that is, ask her out) to reach any scenic spot, and then you can send it when the protagonist prompts you to send it.

Then I went fishing and knew that she had gone to Longdong. Follow the prompts to hit the BOSS step by step. You don't need to replenish blood to do the last trick, but you won't die. Go up and punch the boss, and win.

I hope to succeed at an early date ~ I am married to her. Ask me if you have any questions.