When Ennin was 15 years old, after hearing that Saicho had returned to Japan from Tang Dynasty China and founded Enryaku-ji Temple on Mt. Hiei, he immediately went to Mt. Hiei to study under Saicho.
15歳のとき、唐より最澄が帰国して比叡山延暦寺を開いたと聞くとすぐに比叡山に向かい、最澄に師事する。