While you're in Onomichi, you can take a tram or taxi to Senkoji, or even go there through the north part of town. Once there, head up to the temple and use the small box to the right. The cost is 100 Yen. Then choose 1 of 5 cards, hoping to get the Great Blessing. It's not hard to get. I got it several times while going for Completion List items.