I can't lie how much Ina and all members of HolyMyth, would fit in touhou Universe. Watson would be in outside world along with Maribel and Usami. While everyone else would be in Gensokyo.
With Sumireko*. Since both of them are from the future.
Amelia has a time machine, it would make her easy to visit both Renko and Maribel and talk about Sumireko to them quite easy... unless of course, Amelia has to be careful of not causing a time paradox, or... she gets discovered by someone and decides to ask her a lot of questions...
