We commonly see oil leaks from the steering box of L series.
If left in the weather ,rain water finds its way down the steering shaft and fills the tube with water. It will find its way past the top seal and into the steering box. water goes to the bottom, oil sits on top and leaks out.
Because these are invariably used tractors, the old owners in Japan are not big on maintenance,and as you dont know how they were treated in the past, its best to assume the worst.
The remedy is to dismantle the steering box, clean, replace bearings /seals etc. Reassemble and fill with 90 or 140 grade
steering box oil.
Grease may work for a while, keeping in mind the relatively low hours many small acreage tractors actually work. But its far better to fix it properly, before sectors and recirculating ball carriers fail, which they will do ,when lubricated by water.
Keep the tractor stored under cover, give it some basic maintenance, and it will reward you with many years of hard labour.