The Hidden Diary! (隠された日記！, Kakusareta Nikki!) is an event in Tomba! 2: The Evil Swine Return.
Find the diary that the man in green hid.
In Ranch Area, go up two levels and walk to the right to meet up with a man in green clothes. Talk to him to activate the event.
Then, go down one level and walk all the way to the right to find a chimney covered with snow. Remove the snow with your weapon and jump down. When inside, go to the right to find a wooden box that can be moved. Move it and open the red treasure chest to find the diary. Walk all the way back to the man in green and talk to him to clear the event.