But why? Were they friends or something...?

I don't know Minamitsu-san very well, so it's hard to say, but... Truth be told, they might be closer than you expect.

But, well... If that were the case, Koishi would probably brag to me about it...

So they're probably not that close. Rest easy... hehe.

Although...

Minamitsu-san has actually visited the Palace of the Earth Spirits on her own in the past.