Experts, please tell me!!

Congratulations on reaching the 7th floor of the 'Abyss of Beginnings' and for the lucky pull to get her! The exclusive weapon 'Citrus Stab' is a precious item mainly obtainable through her pickup gacha or the exchange, you know. It's a powerful equipment that enables 3 attacks, so try to aim for the next opportunity without rushing, Hou!

Pulling characters with green stones doesn't come with their weapons. Only when you use stones bought with real money to pull in the gacha will the character appear with their weapon. (Pretty sure that's right, right?)

To get straight to the point, you cannot obtain the Legendary Adventurer's weapon from this 'Yaminabe' gacha. As you can see from the current 'Yoizo' event: - You can get it if the character appears from a bone purchased with paid stones. - You can exchange points for it from the lineup in the exchange shop. However, this 'Yaminabe' gacha only offers bones as an exchange option. Therefore, unfortunately, you won't be able to get the 'Kansashi' this time.

Do I need Kunai to use that 'Senpuku Ban'...?

I just found out today. Kunai are ranged weapons… I thought they were used like daggers…

If you're just trying to advance the story, I think it's better not to get too hung up on specific characters or weapons. If you start wanting the 'strongest XX,' this game can get pretty brutal. I don't have Yuzunamiki, but apparently, she's a character who can deal immense damage with her signature weapon. However, to maximize damage, you'd likely need two fully synthesized signature weapons for both hands. You can't get signature weapons from the current gacha, and even if a pickup appears later, if you're only using green stones, you might have to pull at least 1800 times. Based on past patterns, you can exchange 100 pulls' worth of points for a stage 1 synthesized signature weapon. To get a max-synthesized one, you'd need 9 of those, so 18 for both hands. If you then factor in optimizing star levels and blessings, the possibilities are endless. There are examples like Kassinart's Sword, or signature weapons that became obtainable through a low chance from rare junk obtained from character-specific dispatch requests added later, so there might be other opportunities in the future. Sorry for the long post.