What is that?

[Laurian]

Hello, fellows.

During the last  few months, since I bought my first sword (https://www.militaria.co.za/nmb/topic/49116-my-first-nihonto-a-mumei-uda-school-katana/#comment-516907), I've been trying to enrich my terminology "knowledge base", regarding various aspects of a blade. But, as most of the descriptions available online or in the (still very few) books that I have access to don't come with good enough pictures attached to them, it's pretty hard to figure out what exactly all those things mean.

In the picture below, you have a detail of my newly acquired wakizashi (signed by Fujiwara Masayasu, around Enpo era).

Please let me know what's the whitish line along the hamon called. Is it the nioiguchi or habuchi itself, or something else?

Thanks! 

[Nicolas Maestre]

I'd say it's precisely the nioiguchi, which is named like that since it's almost always made of nioi particles, even in nie deki.

[Laurian]

Merci, Nicolas!