The Grand Seiko Evolution 9 Collection 43.8 mm SLGA015G, also known as the "Ushio" or "Black Stream," is a premier dive watch that exemplifies Grand Seiko's commitment to precision, durability, and aesthetic excellence. Inspired by the Kuroshio Current, one of the largest ocean streams in the world, the deep black dial features a dynamic texture that mimics the powerful and sometimes violent tides of the current. The 43.8 mm high-intensity titanium case is 30% lighter than stainless steel and offers exceptional resistance to scratches and corrosion, ensuring both comfort and longevity. The watch boasts a 200-meter water resistance, making it suitable for professional diving, and is equipped with a unidirectional rotating ceramic bezel for enhanced durability and functionality.

At the heart of the SLGA015G lies the Spring Drive Caliber 9RA5, a movement that combines traditional mechanical watchmaking with electronic regulation to achieve unparalleled accuracy. With an impressive power reserve of approximately 120 hours (5 days) and an accuracy of ±10 seconds per month, the 9RA5 movement ensures precise timekeeping. The movement's design incorporates an "Offset Magic Lever" to reduce thickness and dual-size barrels to expand power reserve capacity while conserving space. Additionally, the movement features enhanced shock resistance and thermo-compensation technology, contributing to its reliability in various conditions.

The SLGA015G is designed with the Evolution 9 philosophy in mind, emphasizing legibility, comfort, and beauty. The dial's high contrast between the hands and markers, along with generous coatings of LumiBrite, ensures excellent readability even in low-light conditions. The case's refined Zaratsu-polished surfaces and curved lugs enhance its ergonomic fit, while the screw-down crown and three-fold clasp with secure lock provide added security and ease of use. With a magnetic resistance of 4,800 A/m and a weight of 150 grams, this timepiece is engineered to withstand the rigors of professional diving while offering a refined aesthetic suitable for various occasions.