It's not a cancel but intended to be part of the imprint/inscription.
It's supposed to read "Koyo/kouyou" (we don't have characters with macrons here, but pronounced more like ''kawwyaww'), reading L to R, meaning "official business". It's supposed to look like this:

That's not any kind of fast scribble but (probably) the work of a clerk who did not know how to write Japanese and was copying the best he could. There is a direction and order to writing characters and this wasn't done here.
Surely this must be original as should be demonstrated by being underneath the machine cancel.
Interesting piece. I don't know why the handwritten part was needed since the stamp was already overprinted as an official (in Tagalog), but there it is.