Birthday: "Yuu is watching me"

The morning after the whole towel fiasco, Miki and Yuu get a call from Yuu's mom, Chiyako, telling Miki to wish Yuu a happy birthday. Miki was so surprised when she found out it was Yuu's birthday. That day she spent her time thinking about what to do for his birthday. She buys food and cake mix for the cake she makes it herself. What will happen between them that day?