Did Giyu Tomioka meet the Hand / Morphed Demon during final selection?
Based on this wiki;


   while Sabito is long dead before the series started, both him and Sabito were best friends as they went through similar situations of losing their family to Demons and bonded well. Later during the Final Selection Exam, Sabito died at the hands of the Hand Demon trying to save his life and others who participated in the exam. Sabito's death caused Giyu to feel so much guilt to the point where he doubted his own abilities as a pillar and rescinds abandoning his position as the Water Pillar.