According to "Koryu-ji Raiyu-ki" (the book on the history of Koryu-ji Temple), his first achievement as busshi was the making of "Nikko and Gakko Bosatsu Ritsuzo" (the standing statues of the Bodhisattva of Sunlight and the Bodhisattva of Moonlight, now designated as important cultural assets) and "Junishinsho Ritsuzo" (the standing statues of Twelve Heavenly Generals, now designated as a national treasure), all of which were crafted in 1064 and were enshrined in Koryu-ji Temple.
長勢の仏師としての事績はまず、康平7年（1064年）に広隆寺の日光・月光菩薩立像（重要文化財）、及び同寺の十二神将立像（国宝）を造立したことが挙げられる（『広隆寺来由記』）。