1. Fucking a Touhou is extremely dangerous, as each of them possess powers capable of killing an inexperienced human very easily.
2. For obvious reasons, trying to fuck a Touhou will make you lose Satori.
3. Since you only possess one dick, it might be very hard to parallelize the fucking of the Touhous. Given the sheer numbers of Touhous, fucking all of them is extremely inefficient.
For all these reasons, I highly recommand you to STOP SEXUALIZING TOUHOUS!!