I was thinking about this last night in bed!
Imagine capture both yonkers and reimu and holding them in solitary confinement. To yonkers, you lock him in chastity and play his most favorite diaper porn 24/7 into his cell so he becomes a raging, horny, tard beast. Dress reimu in a skimpy undertale cosplay and don't let her wipe for weeks. finally when poor yonkers balls are so blue that he is howling in pain, relase him from his cage and put the two of them in the same locked cell ;)