Keine has a spellcard called [Land Sign "Three Sacred Treasures - Sword"] in Imperishable Night. This is a reference to the sword of Kusanagi, one of Japan's three sacred treasures. Rinnosuke received the actual sword from Marisa.
She doesn't, it's just an excuse to... well, panel 4.
That again?Excuse meMr. Shopkeeper, I would like you to give me the Sword of KusanagiOh? You are the one from the village...Hm, you're right...I'm sorry, it has to be worth the value of the item.You're such a bad guy.stripThat is a not-for-sale item. More importantly, don't you think it's brazen of you to ask to have it for free?