The Half Diary is a diary for the two of us to record each other's day in the exchange diary method that we bought and shared with friends and lovers in school. Create a diary in the app, invite friends with an invitation code, select an exchange date in the exchange diary, and record each day during the period. And when the previously set date arrives, the diary written by the other party is disclosed to me and the diary I wrote to the other party, and is saved as one.