One morning while having breakfast Ayato finds an unusual jar of milk. Apparently it’s some sort of Cocogoat milk Ayaka had imported from Liyue. Not wanting it to go bad he decided to drink it himself. That night as he finished up his late night work he started to feel strange. He was then shocked to find his body changing before his eyes. His chest continued to grow larger and large before his eyes. His body becoming more and more feminine. It was then he realized this is what Ayaka had used to grow her breasts in such a short time. He was further shocked that the only thing that hadn’t changed was his genitals.
Aether had come to the Kamisato estate Ayaka had wrote to him that her brother was acting strange. Locking himself in his room and calling for Aether to come help him. Upon arriving he found Ayato now looking like a mature women. Ayato explained the situation and hoped Aethers purification powers could help. As since he didn’t change despite drinking copious amounts of the milk from the source that he must be immune. Aether agreed though as he decided the method he found Ayato already starting it seems that thanks to the transformation Ayato had developed a similar mindset and infatuation as Ayaka. The two indulged each other lost in the experience forgetting all about the purpose. In the end as Aether expected nothing had changed but at this point Ayato could care less.
Later there was quite a stir as it was announced that both Kamisato siblings were now engaged to the traveler.