30th Lattice Defect Forum participated as the organizer was held on Dec. 12-13th as an online conference. Although the conference was expected to cancel this year, taking advantage of the online environment, the conference was held with the content differently from recent years. Thanks to the cooperation of a lot of people, I think it is a great success. After the conference, I received a message from a participant "It can be said that it was a historic conference that will be a narrative for posterity. Especially on the second day, it was a wasteful stimulus to keep it in the forum alone. I think it was something like that.” I realized that the participants had a fulfilling time.