After finding Mugwort, the following material Iyama tasks you to find is Roses. Bring them to him, and Yagami will get another Extract Recipe.
Roses or a single rose can be found very close to Iyama’s location. Head directly north to Hamatika Park, and keep running on the grass, hunting for white glimmers. Pick up all of these, and eventually, you will find a rose. This may take a while, but just keep on the grass, and eventually one will spawn.
Or you can go to Flowers 2 Go, a van shop in Hamakita Park and buy a Rose for 1,280 yen. Either spend your money or spend a bit of time hunting one for free.
If you want to quicken up the process, go into a restaurant and buy some food with the buff Materials+. This increases the rate that materials will spawn in the world, improving the chances of obtaining a rose more speedily.
When a rose is acquired, head back to Iyama to learn Extract Recipe: Willow Snake. The next thing you need to hunt for is Garlic.
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