I thought I would draw the girls having a little fun and just being girls since they are always fighting and putting their lives on the line!
Hong Meiling x Mulan I crossed her with Mulan because they both know martial arts and have Chinese names. I gave her Mulan's flower comb because it seemed to suit her. Her hair color also matches Mulan's dress!
Patchouli Knowledge x Belle They both love books and are very smart. And dark purple hair is close to brown hair? I changed Patchouli's hair ribbons to the bands Belle has.
Nitori Kawashiro x Ariel They both like humans but are initially shy, only observing from afar. I gave her Ariel's clam hair clasps. Nitori's hair color is also that of water and complements Ariel's dress well.
Flandre Scarlet x Rapunzel This one's obvious. They both have a strong power that results in them having to be kept away in some place, ordered there by a relative. Before the other characters arrive, neither of them have had substantive contact with humans. Also, blonde hair tied back (though I made Flandre's side-ponytail longer and weaved in flowers).
Yukari Yakumo x Aurora The sleeping beauties of their respective series. Both heavily associated with sleep, both also sing and both have blonde hair. Obligatory crown of being arguably the most powerful youkai is obligatory.
Okay, I thought about this way too much XD It took a long time to go through each Touhou character, see if they associate with a princess, and pick out the best associations. There were some other ones, but they were weaker to me and I felt 5 was a good number for a group picture like this.
But I had a lot of fun drawing this and it took me out of my comfort zone (I haven't drawn this many characters interacting in one picture in a long time nor have I drawn this many moe girls). It was interesting crossing over 2 of the most iconic styles in Eastern and Western cartoons.