"Hey,it's me again.Let's kill each other." -Nanaya,Battle Moon Wars.
Again,the nightmare_fuel and scary tags can be removed if you want but considering who this yukkuri is based on...
Anyway,I guess I'll probably think of some characteristics of this type.
☢CAUTION!!☢ Large amount of text ahead!
Safe to say that Nanaya types are faster than most/nearly all yukkuri given how quick Nanaya owns Shiki in Kagetsu Tohya as well as his speed in MELTY BLOOD.
Filling....Blood maybe?Things such as custard,chocolate and the like are definitely out of the question with him.Can't really think of a good filling for him...Maybe knives?Nah....
Predator?Hmmm....Probably,thought not being a predator would be more interesting IMO.
Capable of fighting?DEFINITELY.I wouldn't be surprised if Nanaya-types would try to go for the jugular or straight for the paste core for yukkuris.I'd imagine that they'd have sharp teeth to pull those actions off. Very good chance of it using knives like Sakuya-types do,not to mention that Nanaya-types will probably be rather fast.Nanaya-types most likely won't waste too much time with insults and/or hesistate to attack.
Personality....not too sure,however they definitely won't just declare humans to be their slaves or demand sweet-sweets and/or munch-munch.They may ask for them,but will usually leave or (rarely) attack upon refusal. Unlike most yukkuris,Nanaya-types aren't afraid of dying as long as they die a beautiful (read:killed skillfully,artistically,and/or gorey) death.
Relationships with other yukkuri...101% chance that they'll like Sakuya-types,in fact there's a TON of Nanaya X Sakuya art out there. Other types they may like include Tenshis since both of them like suffering,albeit VERY different kinds,as well as Komachis and Shikiekis for obvious reasons.
Okay,that's enough for now.Just remember that all of the above was typed out of boredom and consists of my personal conjectures plus some facts about TYPE-MOON and Touhou.