No. 5 Kai

OTSUKA LOTEC is a Japanese watch brand founded by the independent watchmaker Jiro Katayama.

The model 'No.5 KAI' is equipped with a Japanese MIYOTA movement with an additional satellite hour module designed and manufactured in-house.

To prevent the backlash characteristic of the satellite hour mechanism, the hour disk is driven by a double reduction gear. Additionally, to highlight the static satellite hour mechanism, a considered design has been utilized to ensure that the movement of the mechanics is clearly visible. First, the hour disk directly engages with a ball bearing roller at the 8 o’clock position. The seconds disk at the 5 o’clock position constantly moves regardless of the hour disk’s position, providing a continuous display of its mechanism.

In order to emphasize the three-dimensional shape of the satellite hour mechanism, each component housed within the sapphire crystal, including the “minute index plate” and “hour disk”, is designed to cast distinct shadows.

Originally, the satellite hour mechanism was designed for night clocks to consolidate the hour and minute display at the top of the dial due to visual constraints. The satellite hour mechanism has been adapted in No.5 KAI to address the visual limitations of modern watches—specifically, the issue of part of the watch dial being obscured by a jacket cuff. The revised mechanism consolidates the hour and minute display on the right side of the watch, achieving a visually balanced and refined design.