It was said that the Dragon God resided at Shinsen-en Garden, and that after Shubin of Sai-ji Temple and Kukai of To-ji Temple competed with each other in praying for rain in the year 824, the garden came under the control of To-ji Temple after Kukai was victorious.
神泉苑には竜神が住むといわれ、天長元年（824年）に西寺の守敏と東寺の空海が祈雨の法を競い、空海が勝ったことから以後東寺の支配下に入るようになったという。