|Romanized||Hiyoku no tane|
|Location||Property of Teppei (details unknown)|
|Price||5,000,000 yen per seed|
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The Fertility Seed (肥沃の種 Hiyoku o tane) is described as a "fertilizer for human use", this seed can increase the body's natural healing ability to its maximum. However, due to it containing also a small amount of toxic substances, it also destroys cells before triggering the high-speed recovery, thus possibly proving to be fatal. Individuals who have had their energy stores severely depleted run the risk of dying if administered this seed. Therefore, the utmost caution is needed when handling it. Due to this fact, its usage is restricted by the eight Gourmet Laws. Teppei stated it has a bitter flavor.