The Tokyo Marathon Foundation has signed an official partnership agreement with OujiSeiyaku Co., Ltd. (Tokyo Office: Shibuya, Tokyo) featuring its hair-care brand called “SEIKA ZEN” under the hair care category for the Tokyo Marathon 2026.

“SEIKA ZEN” is a skincare-inspired shampoo that focuses on the hair-washing habits of Japanese people. Combining carefully selected Japanese and Chinese herbal ingredients with modern technology, it helps maintain a healthy scalp environment and promotes voluminous, beautiful hair from the roots. Even after completing a full marathon ("full" called “ZEN” in Japanese), it leaves the scalp feeling refreshed and provides long-lasting deodorizing effects.

Through this partnership, “SEIKA ZEN” aims to provide gentle care for the scalp and hair, which can be easily impacted by sports activities, sweat, and daily stress. By offering daily self-care solutions that help maintain a positive mindset, the brand hopes to empower runners to stay confident and energized throughout their journey.