Sanae's sleeves are detached from her shirt, just like Reimu's. As a result, it is possible to use Sanae as the subject of the "armpit joke" rather than Reimu. However, Sanae armpit jokes are rare compared to Reimu armpit jokes.

https://touhou.fandom.com/w...ae_Kochiya/Fun_Facts
Знаменитые тохо-шутки.