Nanaya's Knife

A treasured blade of the Nanaya family, that Makihisa kept for some reason instead of getting rid of it. Of course, even though it's called a “treasured blade” it isn't actually valuable, it's just a sturdily-built knife. Though, mysteriously it has a complex switchblade design despite its considerable age.
It is a high-quality good with the words “Seven Nights” carved into the handle, clearly marking it as property of the Nanaya family.
In Tsukihime, Kohaku brought this knife to Shiki saying it was a memento left to him by Makihisa, but in reality she had retrieved it from Makihisa's room of her own accord.

Tsukihime Data Collection: Tsukihime Dictionary
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A treasured blade of the Nanaya family, that Makihisa kept for some reason instead of getting rid of it. Of course, even though it's called a “treasured blade” it isn't actually valuable, it's just a sturdily-built knife. Though, mysteriously it has a complex switchblade design despite its considerable age. It is a high-quality good with the words “Seven Nights” carved into the handle, clearly marking it as property of the Nanaya family.
In Tsukihime, Kohaku brought this knife to Shiki saying it was a memento left to him by Makihisa, but in reality she had retrieved it from Makihisa's room of her own accord.
…Kohaku herself never looked to see what was in the box. Perhaps she was expecting it to jog Shiki's memory of his past due to it being property of the Nanaya…?

Tsukihime Dokuhon Plus Period: Tsukihime Dictionary Revised