No. 5 KAI

No. 5 is a name that spans two different ways of telling the time. Ōtsuka Lōtec's original 2012 watch separated the hours, minutes and seconds in a regulator display and included a date. The No. 5 KAI, introduced in 2025, replaced that arrangement with traveling hour discs.

On the KAI, the current hour moves beside a fixed minute scale on the right. Its position along that scale supplies the minutes. Three discs take turns bringing the hours into view, while a separate small disc counts seconds. This is a change to the display's machinery, not simply a new dial.

Katayama gives a practical reason for putting the reading on the right: it can remain visible when a cuff covers part of the watch. That intention led to an unusual arrangement of rotating parts and supports above the base movement. A raised sapphire cover makes room for them.

The automatic Miyota movement supplies power; Ōtsuka's module organizes the hour display. Small bearings support different operations, including the mechanism that changes a disc's numeral. The visible layers are therefore doing different jobs.

The No. 5 KAI keeps the earlier watch's industrial appearance but abandons its method of reading time. Other numbered Ōtsuka watches pursue other arrangements. The common thread is the designer, not a single mechanism repeated beneath different names.