Heading into the 2021 World Championships in Stockholm, Boikova/Kozlovskii were considered one of the favourites to win the pairs title. For the event they prepared a new short program to music from the film "Howl's Moving Castle", which Boikova called "a piece of art and not just a movie." Skating cleanly, they placed first in the short program, winning a gold small medal. In the free skate, Boikova fell on her attempted triple toe loop and on their throw triple flip, and the pair placed fourth in that segment and dropped to the bronze medal position overall.