How is the 100-day anniversary celebrated in Korea?

In Korea, there is a culture of specially celebrating the 100th day since a couple has met. This day is considered an important milestone among lovers, and it is celebrated in various ways. I am curious about what gifts couples typically exchange on their 100th day anniversary. I would like to know if the boyfriend usually takes the lead in planning, or if the couple plans together. Additionally, I wonder what special activities are available for the anniversary, and if there are any fun ideas besides photo shoots. Please share how you celebrated your 100th day anniversary and what preparations you made. If you have any particularly memorable moments or recommendable activities, please let me know.