After gaining independence as an artist, Nagasawa embarked on his unique research into antique masks, which led to the creation of numerous outstanding noh masks. He particularly excelled in crafting female masks, earning high praise for their expressions and coloring. In 1979, he was designated as a “Living National Treasure” (人間国宝, Ningen Kokuhō), a prestigious Japanese honor for individuals who preserve and promote important intangible cultural properties. Throughout his career, Nagasawa Ujiharu remained a prominent contemporary noh mask artisan.