Introducing The New No.5 KAI From the independent Japanese brand Otsuka Lotec

Jiro Katayama, the creator of the independent Japanese watch brand "Otsuka Lotec," is known for his detailed, handmade watches that combine precision and art. Starting his career as an automotive designer, Katayama shifted his focus to watchmaking in 2008 after developing a passion for metalworking. Last year, we discussed his release of The No.7.5, featuring a jumping hour display.

Upon his latest releases, the watchmaker is launching the No.5 KAI, an updated version of the No.5, originally launched in 2012. The watch has a diameter of 40.5 mm, a thickness of 7.6 mm (12.2 mm including the crystal), and is made of stainless steel 316L with a straight-grained finish. It features a display back and offers water resistance up to 30 meters.

The No.5 KAI features a sapphire crystal with anti-reflection and anti-fingerprint coatings. The crown is located at the lower part of the case ( 4 o’clock). When setting the time, it’s important to turn the crown forward to avoid damaging the mechanism.

The watch builds upon the design of its predecessor. Like the original No.5, it uses two Japanese-made ball bearings from MinebeaMitsumi, which is a Japanese manufacturer of mechanical components. The hour disk ball bearing is custom-made for this model. Additionally, the 1.5 mm ball bearing at the center of the seconds disk remains the world’s smallest as of 2025. 

This watch features rotating numeral discs that orbit like satellites, paired with fixed markers to display the time. It is powered by an automatic MIYOTA movement with an in-house satellite “wandering hours” module, operating at 28,800 vph (4 Hz) and offering a power reserve of up to 40 hours. To minimize backlash in the satellite hour mechanism, the hour disc is driven by a double reduction gear. The hour disc interacts with a ball bearing roller at the 8 o'clock position, allowing it to switch instantly twice per hour, mimicking a jumping hour mechanism. The seconds disc at the 5 o'clock position moves continuously, providing a constant view of its mechanism.

The No.5 KAI comes with a black calfskin leather strap and is priced at JPY 748,000, which is approximately AED 17,650.

For more information, you can visit Otsuka Lotec’s official website.