I just realized that there's something a bit off about offering your body to an almost-ten-year-old in order to cheer her up...
Lmao, I thought the same thing. In my head, I'm just like "SHE'S NINE, SHE'S NINE, SHE'S NINE!" Pursuing any kind of sexual intimacy with someone that age is molestation imo. I don't care if her body's more physically mature. In fact, both characters look dangerously underage (though I know Nashi's immortal). It's pretty creepy, but the story's interesting enough to let me overlook those factors.
side note: The Time Merchant looks SO much like Lulu de Morcerf from Shugo Chara. It's uncanny!